SCIP exit routine

The SCIP exit routine is entered when an application program receives any of the following session-control requests by an application program:

CLEAR
Start Data Traffic (SDT)
Request Recovery (RQR)
Set and Test Sequence Numbers (STSN)
BIND
UNBIND.

For CLEAR, RQR, and UNBIND, VTAM® automatically sends a response before the request is presented to the exit routine. For STSN and BIND, the application program must send its own response. For SDT, either the application program or VTAM sends the response, depending on the SDT operand specified on the OPNSEC's NIB. For all these requests except UNBIND, if the application program has no SCIP exit routine, VTAM automatically sends a negative response; for UNBIND, VTAM sends a positive response.

Four of the requests—CLEAR, SDT, STSN, and BIND—are sent only from the PLU to the SLU. Thus, in an application program, those four requests can be received and processed only in an SCIP exit routine at the SLU. RQR is sent only from the SLU to the PLU. Thus, that request is received and processed only in an SCIP exit routine at the PLU. UNBIND can be sent from either the PLU or the SLU. The SCIP exit routine at the PLU is entered on receipt of UNBIND only if the APPL definition statement for the PLU application program is coded with SONSCIP=YES.

You can use SETLOGON OPTCD=HOLD and OPTCD=START to synchronize session setup requests. SETLOGON OPTCD=HOLD causes all BIND requests to be queued and prevents the scheduling of the SCIP exit for session setup requests. When SETLOGON OPTCD=START is issued after SETLOGON OPTCD=HOLD, VTAM schedules the SCIP exit for each queued BIND request. VTAM continues to drive the SCIP exit as usual until the application issues SETLOGON OPTCD=HOLD or SETLOGON OPTCD=QUIESCE.

Note: The SCIP exit is driven for all requests other than BIND regardless of the use of SETLOGON OPTCD=HOLD.

For an SCIP exit routine, information on the request that has been received is available in a read-only RPL provided by VTAM. The RPL resides in read-only VTAM storage and cannot be used by RPL-based macroinstructions. The following are also true for the RPL:

The application program uses SHOWCB, TESTCB, or IFGRPL DSECT to examine the RPL fields (see Figure 2).
The 3-byte user RH field is set (see Operation for inbound RUs for more information).
The CONTROL field identifies the particular session-control request that caused scheduling of the SCIP exit routine.
If SCIP is entered as result of BIND or UNBIND request, AREA contains the address of the BIND or UNBIND RU, and RECLEN and AREALEN fields contain the length of the RU (refer to SNA Formats for a description of the contents of the BIND or UNBIND RU).
CHECK must not be issued for the RPL.

The read-only RPL and any RU pointed to by the AREA field are freed when the exit routine returns to VTAM; any information needed from these areas must be copied before then.

The location of the read-only RPL is provided in the parameter list passed to the exit routine when the routine is scheduled.