In migration mode, the front-end and back-end transactions use LUTYPE6.1 commands just as if the session was an LUTYPE6.1 session. CICS® takes data from the transaction in the normal way, and formats it as an APPC mapped data stream for transmission over the link. At the receiving side, CICS analyses the APPC mapped data stream and presents the LUTYPE6.1 data and function management headers to the receiving transaction.
In general, you will not have to modify existing CICS-to-CICS ISC applications to enable them to run in migration mode on APPC links. A notable exception is the use of the ALLOCATE SESSION command. If your installation previously had individually defined ISC sessions, and your application used the ALLOCATE SESSION command to acquire a specific session, you must change this command to ALLOCATE SYSID.
The ISSUE SIGNAL command is valid for both LU types, but the WAIT SIGNAL command is available only for LUTYPE6.1.
Table 47 compares the commands that you can use for:
As Table 47 shows, migration mode allows you to start adding new function to an application (for example, using ISSUE ERROR or ISSUE ABEND) without converting it entirely to APPC. You can also implement different sync levels by modifying the application to use the CONNECT PROCESS command. Applications not modified to use CONNECT PROCESS will use sync level 2. The migration of an application towards the "pure" APPC level can thus be made stepwise.
To aid migration, the SESSION and CONVID options can be used interchangeably.
If a migration-mode transaction abends, the architected APPC flows take place. How this affects the connected transaction depends where the abend occurs and is often different from what you would expect if the connection were native LUTYPE6.1.
Because APPC uses different modules from LUTYPE6.1, the user exits XZCIN and XZCOUT are not taken for APPC sessions. Any programs making use of these exits on LUTYPE6.1 will need consideration.
Operation | Command | LU6.1 | Migration | APPC |
---|---|---|---|---|
Obtain use of a session | ALLOCATE SESSION | yes | no | no |
Obtain use of a session | ALLOCATE SYSID | yes | yes | yes |
Build an LUTYPE6.1 attach FMH | BUILD ATTACHID | yes | yes | no |
Start a partner transaction | SEND | yes(1) | yes(4) | no |
Start a partner transaction | SEND ATTACHID | yes(2) | yes(5) | no |
Start a partner transaction | SEND FMH | yes(3) | yes(6) | no |
Start a partner transaction | CONNECT PROCESS | no | yes(7) | yes(7) |
Retrieve information about how the transaction was initiated | EXTRACT ATTACH | yes | yes | no |
EXTRACT PROCESS | no | yes | yes | |
Send data | SEND | yes | yes | yes |
Send further LUTYPE6.1 FMHs | SEND ATTACHID | yes | yes | no |
Send further LUTYPE6.1 FMHs | SEND FMH | yes | yes | no |
Receive LUTYPE6.1 FMHs | EXTRACT ATTACH | yes | yes | no |
Receive data | RECEIVE | yes | yes | yes |
Send and receive data | CONVERSE | yes | yes | yes |
Program error | ISSUE ERROR | no | yes | yes |
Abend conversation | ISSUE ABEND | no | yes | yes |
Request change of direction | ISSUE SIGNAL | yes | yes | yes |
Await SIGNAL condition | WAIT SIGNAL | yes | no | no |
Synchronize | Level 0 | no | yes(8) | yes |
Synchronize | Level 1
SEND CONFIRM ISSUE CONFIRMATION |
no no |
yes(8) yes |
yes yes |
Synchronize | Level 2
SEND CONFIRM ISSUE CONFIRMATION SYNCPOINT SYNCPOINT ROLLBACK |
no no yes no |
yes(8) yes yes yes |
yes yes yes yes |
Notes on migration of
LUTYPE6.1 programs:
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