CHKP (basic) call
A basic Checkpoint (CHKP) call is used for recovery purposes.
Format
>>-CHKP--+-i/o_pcb-+--i/o_area--------------------------------->< '-aib-----'
| Call Name | DB/DC | DBCTL | DCCTL | DB Batch | TM Batch |
|---|---|---|---|---|---|
| CHKP | X | X | X | X | X |
Parameters
- i/o pcb
- Specifies the I/O PCB, the first PCB address in the list passed to the program, to use for this call. It is an input and output parameter.
- aib
- Specifies the application interface block (AIB) that is used for
the call. This parameter is an input and output parameter. The following fields must be initialized in the AIB:
- AIBID
- Eye catcher. This 8-byte field must contain DFSAIBbb.
- AIBLEN
- AIB lengths. This field must contain the actual length of the AIB that the application program obtained.
- AIBRSNM1
- Resource name. This 8-byte, left-justified field must contain the PCB name IOPCBbbb.
- AIBOALEN
- I/O area length. This field must contain the length of the I/O area that is specified in the call list.
- i/o area
- Specifies the I/O area to use for the call. This parameter is an input and output parameter. For the CHKP call, the I/O area that contains the 8-character checkpoint ID. If the program is an MPP or a message-driven BMP, the CHKP call implicitly returns the next input message into this I/O area. Therefore, the area must be long enough to hold the longest message that can be returned.
Usage
In transaction management application programs, the basic CHKP call can be used to retrieve the conversational SPA or the initial message segment that was queued before the application was scheduled. The CHKP call commits all changes made by the program and, if your application program abends, establishes the point at which the program can be restarted.
Restrictions
CPI Communications driven application programs cannot issue a basic CHKP call.