Virtual Machine Tool Set

VM Multiple Logical Terminal Session Emulator


VMRSM Index Page.

VMRSM Installation Page.




                                                                                
                                                                                
         1.0   Program Description                                              
               1.1   Design Theory                                              
               1.3   Program Flow Main                                          
               1.4   Program Flow (Secondary Guest Facility)                    
               1.5   Program Flow (I/O to dialed terminal)                      
               1.6   Recovery after Normal/Test Key depressed.                  
               1.7   Updating of non-displayed session                          
                                                                                
         2.0   Installation and Operation                                       
               2.1   Define Virtual Machine for MLTS                            
               2.11  Performance Recommendations                                
               2.2   Service Machine PROFILE EXEC                               
               2.3   Invocation EXEC                                            
               2.4   Operational Commands and PF keys                           
                                                                                
                                                                                
         4.0   Program Product Exceptions                                       
                                                                                
         5.0   Error Messages                                                   
                                                                                
         9.0   Disclaimer                                                       
                                                                                
                                                                                
11.1     Design Theory                                                          
                                                                                
                                                                                
       This program provides a facility to simulate much of the functionthe     
     of the multiple logical terminal features of the IBM 3174 Terminal         
     Control Unit via the VM Logical Device Facility.                           
       A single virtual machine acts as the MLTS server.  This server will      
     will establish and maintain up to 8 logical terminal sessions with CP,     
     drive all I/O to the dialed port, and maintain save areas for each         
     logical session.                                                           
                                                                                
     * NOTE * NOTE * NOTE * NOTE * NOTE * NOTE * NOTE * NOTE * NOTE * NOte *    
     ** CURRENTLY ONLY 4 DIALED PORTS ARE DEFINED AND SUPPORTED                 
                                                                                
       When a terminal 'DIALS' in to the service machine you receive the        
     normal connection message posted by CP.  Upon the first I/O attention      
     interrupt, the MLTS facility performs a DIAGNOSE 8C to access the          
     device dependant characteristics of the dialed device.  The CTS Logo       
     will then be displayed and prompt the user for the number of concurrent    
     logical sessions desired (default is 2), and the selection of a session    
     TOGgle key (default is PA2), and the optional selection of a backward      
     toggle key (no default).      After this point a logical device            
     INITIATE builds the first session based upon the return of the diagnose    
     and the user selected parameters.                                          
                                                                                
       Each dialed port will have up to 8 logical sessions built.  A            
     buffer is kept for each session and this buffer is updated whenever        
     an ACCEPT of data is required by CP for this logical display.  The         
     current session display is updated upon the terminal surface.              
       Upon toggling through the logical sessions, before the next session      
     is displayed, the currently displayed session is retrieved from the        
     display surface by way of a READ BUFFER command and saved with status      
     in a unique buffer.  Some extended features are preserved.  Following      
     the save, the next sequential session established is then restored         
     from its storage buffer and presented to the physical display surface.     
     If a session is updated while it is not the session being displayed        
     then up to 32 updates along with the initial saved screen will be          
     saved (given the updates can be accomodated by the storage buffers)        
                                                                                
                                                                                
       All functions performed on the displayed session are the same as         
     would be without the MLTS except for the "jump-keys".  These keys have     
     to be reserved for exclusive use by the MLTS to signal session jumps.      
                                                                                
       Detachment of your sessions from the MLTS server is accomplished         
     by disconnecting or logging off each of the sessions, then entering        
     the MLTS command "LDEVEXIT" from the VM Logo (or next screen).             
                                                                                
       Disconnection from the MLTS server is accomplished the MLTS command      
     "LDEVDISC" from the VM Logo (or next screen).                              
                                                                                
11.3     Program Flow Main                                                      
                                                                                
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
                                                                Facility        
                                  Define GRAFs and                              
                                  initialize program.                           
                                  <...WAIT...>                                  
                                                                                
    DIAL                ------>   I/O Interrupt                                 
                                                                                
    Post dialed by CP             Prepare for ATTN                              
                                  <...WAIT...>                                  
                                                                                
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                                  Perform DIAG 8C.                              
                                  Determine 3270 type                           
                        <------   Write CTS LOGO                                
                                  Post LDEV characteristics                     
                                  <...WAIT...>                                  
                                                                                
    Enter or PF,PA key  ------>   I/O Interrupt                                 
                                                                                
                        <----->   Perform Read Mod                              
                                  Set "toggle" keys                             
                                  <...WAIT...>                                  
                                                                                
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                                  Perform INITIATE       ----->  LogDev Fac     
                                  Update dialed device                          
                                  matrix.                                       
                                  <...WAIT...>                                  
                                                                                
                                  NEWSESS:                                      
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
                                  Perform ACCEPT data.   <-----  LogDev Fac     
                                                                                
    VM Logo or other    <------   Write data recvd                              
    displayed.                    to dialed terminal.                           
                                  <...WAIT...>                                  
                                                                                
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                        <----->   Perform Read Mod                              
                                                                                
                                  Perform PRESENT data   ----->  LogDev Fac     
                                  <...WAIT...>                                  
                                                                                
                                  External Interrupt     <-----  LogDev Fac     
                                  <...WAIT...>                                  
         .                        .                              .              
         .                        .                              .              
         .                        .                              .              
                                                                                
    Toggle Key          ------>   I/O Interrupt                                 
                                  AID 'xx'                                      
                        <----->   Read Buffer                                   
                                  Store session buffer.                         
                                  Set up for next session.                      
                                  If previous session exist                     
                                     Goto RESTSESS.                             
                                  Perform DIAG 8C.                              
                                  Perform INITIATE       ----->  LogDev Fac     
                                  Update dialed device                          
                                  matrix.                                       
                                     Goto NEWSESS.                              
                                                                                
                                  RESTSESS:                                     
                                  Restore next seq session                      
    Previous Display    <------   Write to Dialed device.                       
                                  <...WAIT...>                                  
                                                                                
    'ldevexit'          ------>   I/O Interrupt                                 
                                                                                
                                  Perform Read Mod                              
                                  Perform TERMINATE      ----->  LogDev Fac     
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
     Dropped Msg        <------   CP RESET GRAF                                 
     VM LOGO displayed            <...WAIT...>                                  
                                                                                
                                                                                
                                                                                
    'ldevdisc'          ------>   I/O Interrupt                                 
                                                                                
                                  Perform Read Mod                              
                                                                                
     Dropped Msg        <------   CP RESET GRAF                                 
     VM LOGO displayed            <...WAIT...>                                  
                                                                                
                                                                                
11.4     Program Flow (Dialed into second service machine such as VTAM,         
         PASSTHRU, CICS, etc)                                                   
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
                                                                Facility        
                                  Define GRAFs and                              
                                  initialize program.                           
                                  <...WAIT...>                                  
                                                                                
    DIAL                ------>   I/O Interrupt                                 
                                                                                
    Post dialed by CP             Prepare for ATTN                              
                                  <...WAIT...>                                  
                                                                                
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                                  Perform DIAG 8C.                              
                                  Perform INITIATE       ----->  LogDev Fac     
                                  Update dialed device                          
                                  matrix.                                       
                                  <...WAIT...>                                  
                                                                                
                                  NEWSESS:                                      
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
                                  Perform ACCEPT data.   <-----  LogDev Fac     
                                                                                
    VM Logo or other    <------   Write data recvd                              
    displayed.                    to dialed terminal.                           
                                  <...WAIT...>                                  
                                                                                
    DIAL Command        ------>   I/O Interrupt                                 
                                                                                
                        <----->   Perform Read Mod                              
                                                                                
                                  Perform PRESENT data   ----->  LogDev Fac     
                                  <...WAIT...>                                  
                                                                                
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
                                  Perform ACCEPT data.   <-----  LogDev Fac     
                                                                                
    VTAM, Passthru      <------   Write data recvd                              
    or other logo                 to dialed terminal.                           
                                  <...WAIT...>                                  
         .                        .                              .              
         .                        .                              .              
                                                                                
    UNDIAL, RSET        ------>   I/O Interrupt                                 
    (disconnect)                                                                
                        <----->   Perform Read Mod                              
                                                                                
                                  Perform PRESENT data   ----->  LogDev Fac     
                                  <...WAIT...>                                  
                                                                                
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
                                  CP Requests Terminate  <-----  LogDev Fac     
                                                                                
    (unlock keyboard)   <------   Write unlock datastream                       
                                  to dialed terminal.                           
                                  <...WAIT...>                                  
                                                                                
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                                  Perform DIAG 8C.                              
                                  Perform INITIATE       ----->  LogDev Fac     
                                  Update dialed device                          
                                  matrix.                                       
                                  <...WAIT...>                                  
                                                                                
                                                                                
                                                                                
                                                                                
11.5     Program Flow (I/O to dialed terminal)                                  
                                                                                
         READ Operation:                                                        
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
    Enter Key           ------>   I/O Interrupt                                 
                                                                                
                        ------>   Perform Read Mod                              
                                  if CC^0 then test and re-drive                
                                                                                
                                 <..WAIT for CE+DE or DE..>                     
                                                                                
                        ------>   I/O Interrupt(s)                              
                                                                                
                                  Perform PRESENT                               
                                                                                
                                                                                
         WRITE Operation:                                                       
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
                        <------   Perform Write                                 
                                  if CC^0 then test and re-drive                
                                                                                
                                 <..WAIT for CE+DE or DE..>                     
                                                                                
                        ------>   I/O Interrupt(s)                              
                                                                                
                                  <...WAIT...>                                  
                                                                                
                                                                                
11.6     Program Flow (Recovery after NORMAL/TEST toggle or Unit Exception)     
                                                                                
         WRITE Operation:                                                       
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
                                                                                
    NORMAL/TEST toggle  ------>                                 Dialed device is
                                                                   "dropped"    
                                                                                
                        <------   Perform Write                                 
                                  if CC^0 then test and re-drive                
                                                                                
                                 <..WAIT for DE..>                              
                                                                                
    Dial Command        ------>   I/O Interrupt(s)                              
                                                                                
                                  <....DE....>                                  
                                                                                
                                  Resume Logic with last                        
                                  active session displayed                      
                                                                                
                                                                                
                                                                                
11.7     Updating of non-displayed session                                      
                                                                                
                                                                                
    TERMINAL                      SERVICE MACHINE               CP Logical Dev  
                                                                Facility        
                                                                                
                                  Non-displayed session                         
                                  External Interrupt     <-----  LogDev Fac     
                                                                                
                                  Perform ACCEPT data.   <-----  LogDev Fac     
                                                                                
                                  If number of msgs queued                      
                                  is > max, and msg will not                    
                                  overrun storage buffer then                   
                                  Update stored buffer                          
                                  with ACCEPTed data.                           
                                  <...Continue...>                              
                                  Else purge msg queue and                      
                                  Update stored buffer                          
                                  with ACCEPTed data.                           
                                  <...Continue...>                              
                                                                                
                                                                                
    Toggle Key          ------>   I/O Interrupt                                 
                                  AID 'xx'                                      
                        <----->   Read Buffer                                   
                                  Store session buffer.                         
                                  Set up for next session.                      
                                  If previous session exist                     
                                     Goto RESTSESS.                             
                                  Perform DIAG 8C.                              
                                  Perform INITIATE       ----->  LogDev Fac     
                                  Update dialed device                          
                                  matrix.                                       
                                     Goto NEWSESS.                              
                                                                                
                                  RESTSESS:                                     
                                  Restore next seq session                      
    Previous Display    <------   Write to Dialed device                        
                                  any queued messages.                          
                                  <...WAIT...>                                  
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
      OPERATION:   Start:    execute LDEVMLTS                                   
                                                                                
                   Stop:     Enter:  LDEVTERM                                   
                                                                                
                                                                                
                                                                                
                   Dial into service machine running LDEVMLTS                   
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
12.1     Define Virtual Machine for MLTS                                        
                                                                                
         This assumes that the LDEVMLTS components are on the 19F disk.         
                                                                                
         Console for MLTS Service Machine must be at address 01F or 009.        
                                                                                
                                                                                
                                                                                
  USER LVM1 ANYPASS 4M 8M G                                             12100941
   ACCOUNT 702 LVM1                                                     12100941
   IPL CMS PARM AUTOCR                                                  12100941
   SHARE REL 1000                                                               
   CONSOLE 009 3270 T                                                   12100941
   SPOOL 00C 3505 *                                                     12100941
   SPOOL 00D 3525                                                       12100941
   SPOOL 00E 3203 A                                                     12100941
   LINK MAINT 190 190 RR                                                12100941
   LINK MAINT 19D 19D RR                                                12100941
   LINK MAINT 19E 19E RR                                                12100941
   LINK MAINT 19F 19F RR                                                12100941
  MDISK 191 3375 81 1 VMSRES MR READ                                    12100941
                                                                                
                                                                                
                                                                                
12.11    Performance Recommendations                                            
                                                                                
                                                                                
         Lock MLTS Service Machine pages 0 and 20 thru 2A.                      
                                                                                
         Set SHARE so that MLTS receives service at a level higher              
         than logical user sessions.                                            
                                                                                
                                                                                
                                                                                
                                                                                
12.2     Service Machine PROFILE EXEC                                           
                                                                                
         This assumes that the LDEVMLTS components are on the 19F disk.         
                                                                                
                                                                                
 /* Profile Exec for LDEVMLTS Service Machine */                                
 TRACE ALL                                                                      
 'SET RDYMSG SMSG'                                                              
 'SET EMSG ON'                                                                  
 'CP SET RUN ON'                                                                
 'CP AUTOREAD OFF'                                                              
 'CP TERM HILIGHT ON'                                                           
 'CP SCREEN VMOUT RED NONE INAREA YELLOW NONE'                                  
 'CP SCREEN STATAREA PINK NONE CPOUT TUR NONE INREDISP WHIT NONE'               
 'CP SP 00C CL *'                                                               
 'CP SP PRT * '                                                                 
 'ACC 19F W'                                                                    
 'CP SET PF12 RETRIEVE'                                                         
 'CP SET PF24 RETRIEVE'                                                         
 'EXECIO 1 CP (STRING QUERY ' USERID()                                          
 parse pull . . where .                                                         
 if where = "DSC" then                                                          
    do                                                                          
    queue 'LDEVMLTS'                                                            
    end                                                                         
 EXIT 0                                                                         
                                                                                
                                                                                
                                                                                
                                                                                
12.3     Invocation EXEC                                                        
                                                                                
                                                                                
 /*  Last Update:   01-13-90            */                                      
 TRACE off                                                                      
 'CP SET EMSG OFF'                                                              
 'CP SET MSG OFF'                                                               
 'CP SET IMSG OFF'                                                              
 n = 0                                                                          
 ADDRESS COMMAND 'EXECIO * CP (STRING Q PF '                                    
 DO WHILE (QUEUED() > 0)                                                        
    n = n + 1                                                                   
    PARSE PULL pfk.n a1.n a2.n a3.n a4.n a5.n a6.n a7.n a8.n .                  
 END                                                                            
 'CP TERM BRKKEY PA1'                                                           
 DESBUF                                                                         
 'CP SET RUN OFF'                                                               
 'CP SET PF12 RET'                                                              
 'vmfclear'                                                                     
 LDEVMLTS                                                                       
 'CP SET RUN ON'                                                                
 DO i = 1 to n                                                                  
    'EXECIO 0 CP (STRING SET 'pfk.i a1.i a2.i a3.i a4.i a5.i a6.i a7.i a8.i     
 END                                                                            
 'CP SET EMSG ON'                                                               
 'CP SET MSG ON'                                                                
 'CP SET IMSG ON'                                                               
 'CP TERM HILIGHT ON'                                                           
 RETURN 0                                                                       
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
12.4     Operational Commands for the MLTS Service Machine                      
                                                                                
   The Service Machine console must be defined at either x'0009' or x'00        
                                                                                
   The logical device ports that will be defined by LDEVMLTS will be:           
                                                                                
         x'0010'                                                                
         x'0011'                                                                
         x'0012'                                                                
         x'0013'                                                                
         x'0014'                                                                
         x'0015'                                                                
         x'0016'                                                                
         x'0017'                                                                
         x'0018'                                                                
         x'0019'                                                                
         x'001A'                                                                
         x'001B'                                                                
         x'001C'                                                                
         x'001D'                                                                
         x'001E'                                                                
         x'001F'                                                                
                                                                                
                                                                                
                                                                                
    Automatic Approach:                                                         
    Build one or more service virtual machines based on supplied example.       
    Create a PROFILE EXEC based upon supplied sample.  This will start  .       
    the MLTS service facility if autologged and disconnected.                   
    Have autolog performed by your AUTOLOG1 machine or done manually.   .       
                                                                                
                                                                                
    Manual Approach:                                                            
    Build one or more service virtual machines based on supplied example.       
    Logon to MLTS Service machine.                                              
                                                                                
                      Start:    execute LDEVMLTS                                
                                                                                
                                (The time and version number will display)      
                                                                                
                                then enter    #CP DISCONNECT                    
                                                                                
                                                                                
                      Stop:     Logon to MLTS Service Machine                   
                                                                                
                                #CP BEGIN                                       
                                                                                
                                Enter:  LDEVTERM                                
                                                                                
                                                                                
                                                                                
             Dump Trace Data:   Logon to MLTS Service Machine                   
                                                                                
                                #CP BEGIN                                       
                                                                                
                                Enter:  LDEVTRAC                                
                                                                                
                                                                                
1   Recovery                                                                    
                                                                                
    In event of 'NORMAL/TEST' toggle, and dialed device is dropped from         
    the service machine:                                                        
                                                                                
                     DIAL the MLTS Service Machine (ie LVM1)                    
                     (last displayed session should be re-established)          
                                                                                
                                                                                
    In event of 'hang' condition or other failure then:                         
                                                                                
                     LOGON to the MLTS Service Machine (ie LVM1)                
                     #CP SYSTEM CLEAR                                           
                     #CP SYSTEM RESET                                           
                     #CP IPL CMS                                                
                                                                                
    (To restart see above MANUAL APPROACH)                                      
                                                                                
                                                                                
    Exception event messages will be logged on the MLTS Service Machine         
    console when in "CONNECT" mode.  No messages are logged when 'DSC'          
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
1   For the Dialed user terminals                                               
                                                                                
                                                                                
    Dial the  MLTS_Service_Machine.                                             
                                                                                
    CP will post the 'DIALED TO XXXXXXX as VDEV' message.                       
                                                                                
                                                                                
    Hit Enter,  the CTS Logo will be displayed.  Logical Device terminal        
    characteristics as determined by the Diagnose X'8C' are posted at the       
    upper right of the logo screen.                                             
                                                                                
    The virtual dialing address is assigned and posted at the upper righ        
                                                                                
    The date and time of the last CMS IPL performed on the Service Machi        
    appear just above the logo.                                                 
                                                                                
    At this time the user                                                       
    is prompted to select the number of concurrent logical sessions they        
    desire (2-8, default is 2) and the user may select the PA or PF key         
    that is to be used as the "session toggle" hot key.  This key will          
    be used to jump to the next session and cannot be used by the under-        
    lying application. The default PA2 becomes armed to toggle between          
    two sessions if the user hits the ENTER key with no selectables.            
                                                                                
    Constraint:  To select a number of sessions greater than the default        
    the user MUST use either a PF key as the 'toggle' key or accept the         
    PA2 default as the 'toggle' key.  Explicit choosing of PA1, PA2 or          
    PA3 as the 'toggle' key will restrict you to the DEFAULT number of          
    sessions.                                                                   
                                                                                
    Also at this time the user is prompted to optionally select the PF key      
    that is to be used as the session "backward" toggle key.  This key will     
    be used to jump to the previous session and cannot be used by the under-    
    lying application.  No default is armed in the event of no selection        
                                                                                
    Constraint:  Backward toggle must be a PF Key or PA Key.                    
    The acceptable entries are  PFxx  ,where xx is 01 thru 24.                  
                                PAy   ,where y  is 1  thru 3.                   
                                                                                
                                                                                
    Hit Enter,  the VM Logo will appear.  The first logical session has         
    been established and further sessions can be created using the              
    "session toggle" keys.                                                      
                                                                                
                                                                                
    Hit session toggle key to establish next multiple logical session.          
      A VM Logo will appear for each new logical session.                       
                                                                                
                                                                                
    Each session toggle will save the current displayed session and             
      sequence to the next session in round-robin fashion.  (1-2-3-...-1)       
      or backward toggling (-4-3-2-1-...-4).                                    
      The current display and up to 32 queued update messages are saved.        
                                                                                
                                                                                
1Termination of any one Logical Sessions:                                       
                                                                                
                                                                                
 (1) If logged on to a virtual machine:                                         
        Disconnect or Logoff                                                    
        You will receive normal CP messages                                     
        Upon enter the VM Logo will appear.                                     
                                                                                
                                                                                
 (2) If dialed in to a virtual machine:                                         
        Use normal disconnect sequence as you would without MLTS.               
        (such as VTAM, PASSTHRU, VSE CICS)                                      
                                                                                
        Upon CP RESET done by above applications your keyboard may lock.        
        Press RESET key followed by Enter                                       
                                                                                
        If NOT LOCKED then just press Enter a second time                       
        Upon enter the VM Logo will appear.                                     
                                                                                
                                                                                
                                                                                
                                                                                
Termination of all Logical Sessions and detachment from Service Machine        
                                                                                
                                                                                
    First Logoff or Disconnect from each logical session leaving the            
    VM Logo displayed on each.                                                  
                                                                                
                                                                                
    On ANY session displaying the VM LOGO, from field:                          
                                                                                
                                                                                
        'COMMAND  ===> ldevexit'                                                
                                                                                
                                                                                
    -OR-                                                                        
                                                                                
    The screen following an ENTER stroke from the VM LOGO:                      
                                                                                
                                                                                
                                                                                
                                                                                
    Enter:          This will terminate all logical sessions between            
   'LDEVEXIT'       this port and CP, then the MLTS service machine will        
      or            perform a CP RESET of this DIALED port.                     
   'ldevexit'       This commands can be entered at the lower left-hand         
                    corner of the cleared VM Logo display surface.              
                                                                                
                                                                                
    Enter:          This will preserve the logical sessions between             
   'LDEVDISC'       this port and CP, then the MLTS service machine will        
      or            perform a CP RESET of this DIALED port.                     
   'ldevdisc'       This commands can be entered at the lower left-hand         
                    corner of the cleared VM Logo display surface.              
                                                                                
                                                                                
                                                                                
                                                                                
Emergency Termination from Multiple Logical Device Service Facility.           
                                                                                
                                                                                
    In the event of an unrecoverable 'hang' condition in which the              
    MLTS service machine becomes disabled for interrupts (or just plain         
    sick) then:                                                                 
                                                                                
       Use the NORMAL/TEST hardware switch of your terminal to DROP             
       all sessions with the MLTS.                                              
                                                                                
    The logical sessions may enter FORCED / DISCONNECT state.                   
    or the equivalent state you would experience if one performed a             
    NORMAL/TEST against any logged/dialed session.                              
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
Program Product Exceptions                                                   
 * * *          Known Problem Areas and Constraints           * * *             
                                                                                
                                                                                
 --If any of the logical session screens are updated while they are in          
   the MLTS saved buffers, ..AND..the number of queued messages has             
   exceeded the limit,..OR..the queued messages will overrun the queued         
   message buffers, THEN only the most recent 3270 datastream is                
   preserved for re-display when you hot-key back to that session.              
                                                                                
 --An application that sits behind the Logical Session (such as you are         
   dialed into CICS) will not be able to perform a screen read operation        
   to one of the logical screens if that screen is not currently on the         
   physical terminal.  In most applications this is not a problem since         
   the request for a read is ACCEPTED by the MLTS Service Machine in the        
   form of a READ I/O data stream command which will be queued until the        
   user toggles to that session.                                                
                                                                                
 --Extended field attributing and some extended color is not preserved when     
   saving the contents of the display surface during 'hot-key' jumping.         
   Field attributes and extended color is usually restored upon the next        
   write to the terminal by the application.                                    
                                                                                
 --Lost logical device can occur during disconnect, reset or logoff of a        
   MLTA session who has another MLTA session as a secondary console.            
   The lost session will not accept I/O since it is marked severed in CP        
   and active in the MLTA logical device tables.                                
                                                                                
 --Disc logical device can occur during shutdown processing of a second         
   level VM Guest.  The CP console for the VM Guest posts the normal            
   warm start saved and RRR.III.NNGG messages, then first level CP issues       
   a CP TERMINATE which causes the MLTS to detach that logical session.         
   The recovery action is to manually detach the logical device from            
   the MLTS machine (XA only).                                                  
                                                                                
 --If an underlying application driving a session places the logical            
   terminal in a inhibit mode, and that logical session becomes the             
   displayed physical session, then the inhibit is preserved and honored        
   This will prevent toggling until the inhibit is cleared using 3270           
   conventions, such as Erase/Write from the underlying application.            
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
15.0     Messages that will appear on MLTS service console                      
                                                                                
 Start Message:                                                                 
   YY/MM/DD L  Enter 'LDEVTERM' to terminate                                    
                                                                                
 Stop  Message:                                                                 
   Termination Complete, returning to CMS                                       
                                                                                
 Unknown Request Message:                                                       
    Undetermined Request,  ...CONTINUING...                                     
                                                                                
 Disconnection Message:                                                         
   DISCONNECT from logical sessions                                             
                                                                                
 Exit Message:                                                                  
   EXIT from logical sessions                                                   
                                                                                
                                                                                
                                                                                
 Logical Device Operation          Condition Code /    Logical Device           
 Operation Exceptions              Return Code pair    Address                  
 ------------------------          ----------------    --------------           
 INITIATE                          CC  RC              cccc                     
 REINIT   (Re-Initiate)            CC  RC              cccc                     
 ACCEPT                            CC  RC              cccc                     
 PRESENT                           CC  RC              cccc                     
 TERMINAT (MLT Terminate)          CC  RC              cccc                     
 CPTERMIN (CP Terminate)           CC  RC              cccc                     
                                                                                
 **See description of codes in IBM Logical Device Facility manual.              
                                                                                
                                                                                
 MLTS      Device I/O                                                           
 Operation Exceptions              Return Code         Address                  
 ------------------------          ----------------    --------------           
 SCRERR   (Screen Error)               RC              01F or 009               
                                       0A = Device Not Operational              
                                       0B = Channel Path Problems               
                                       0D = Unit Exception                      
                                                                                
                                                                                
 Logical Device Support Facility External Interrupt Reason Codes                
                                                                                
 IRCODE=0      External Interrupt Return Code from Diagnose 7C                  
 IRCODE=1      External Interrupt Return Code from Diagnose 7C                  
 IRCODE=2      External Interrupt Return Code from Diagnose 7C                  
 IRCODE=3      External Interrupt Return Code from Diagnose 7C                  
 IRCODE=4      External Interrupt Return Code from Diagnose 7C                  
 IRCODE=5      External Interrupt Return Code from Diagnose 7C                  
 IRCODE>5      External Interrupt Return Code from Diagnose 7C                  
 CPTERM ?      Terminate Failed because logical device not in matrix.           
 UNEX INT      Unexpected Interrupt occurred                                    
 NO LDEV       No logical device listed                                         
 NO SLOT       Logical device matrix slot position invalid.                     
 PFUNPURG      Last PRESENT function has been purged.                           
 TRANSERR      CP posted error in transmission.                                 
                                                                                
                                                                                
 
 
     Disclaimer                                                                 
                                                                                
       In no event  will Licensor or its representatives be liable to the       
     Licensee  or any other party for  any loss, including  time,  money,       
     good will  and  consequential damages, which may arise from the use,       
     operation, modification or interpretation of the Licensed Program by       
     the Licensee.  CTS does not warrant that the functions contained in        
     the program will meet the customer's requirements or will operate in       
     combinations which may be selected for user by the customer, or that       
     the operations of the program will be uninterrupted or error free, or      
     that all program defects will be corrected.                                
                                                                                
                                                                                
                                                                                

                                                                                
                                                                                
                                                                                

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