gtpi1m18 | System Installation Support Reference |
User exit routine UCCECB is invoked whenever a new entry control block
(ECB) is created, if the exit point named ECB is active. Exit point ECB
is located in the ECB creation routine contained in CSECT CCNUCL
(CHSZ). UCCECB provides the ability to examine the origin (via the ECB
format flag) of all ECBs and to subsequently track individual ECBs.
General Conditions at Entry
The registers at entry to UCCECB are:
- R0-R8
- The contents are unknown because the ECB exit point is in the ECB creation
subroutine, and therefore the contents of these registers are dependent on the
calling routines.
- R9
- Address of the ECB that was just created.
- R11-R15
- See User Exit Routines - Common Entry Conditions.
System Conditions at Entry
- System state
- Supervisor
- System mask
- Masked for I/O
- Protect key
- 0
- Address Space
- SVM.
Programming Considerations at Entry
- Because the ECB exit point is in a subroutine called from more than 1
point in the control program, user processing must not give up control,
and must return to the NSI contained in register 14. The ECB
cannot be exited and control cannot be passed to the CPU loop (Task
Dispatcher).
- At entry to UCCECB, the ECB has been allocated and initialized, including
the ECB format flag at label CE1FLG in the ECB. The format flag value
can be used to determine the type of ECB (for example, control transfer, SNA
input message, and others).
- At entry to UCCECB, the process control block associated with the ECB has
been allocated. The default group ID and user ID (IPROC_GID and
IPROC_UID) can be modified at this point. The group ID and user ID are
used by the file system to handle file permissions. You can find the
address of the process control block at CE2PROC in page 2 of the ECB.
The IPROC DSECT maps the process control block fields.
- The environment variables can be set to specify the initial current
working directory, the standard input (stdin) file, the standard output
(stdout) file, and the standard error (stderr) file.
- The following fields in the ECB can be modified:
- Maximum amount of storage for the C language stack (CE2MHSF)
- Maximum amount of storage for TPF heap storage (CE2MPF)
- Initial stack allocation (CE2ISAS)
- Stack increment (CE2SISZ).
- See User Exit Routines - Common Entry Conditions.
- See User Exit Routines - Common Programming Considerations for other considerations.
Programming Considerations on Return
See User Exit Routines - Common Return Conditions.
General Conditions on Return
See User Exit Routines - Common Return Conditions.