CHKP (symbolic) call
A symbolic Checkpoint (CHKP) call is used
for recovery purposes. If you use the symbolic Checkpoint call in
your program, you also must use the XRST call.
The ODBA interface does not support this call.
Format
| 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 for the call. This parameter is an input
and output parameter. A symbolic
CHKPcall must refer to the I/O PCB. - aib
- Specifies the AIB for the call. This parameter is an input and
output parameter. These 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 specified in the call list.
- i/o area length
- This parameter is no longer used by IMS. For compatibility reasons, this parameter must be included in the call, and it must contain a valid address. You can get a valid address by specifying the name of any area in your program.
- i/o area
- Specifies the I/O area in your program that contains the 8-byte
ID for this checkpoint. This parameter is an input parameter. If the
program is a message-driven BMP, the
CHKPcall implicitly returns the next input message into this I/O area. Therefore, the area must be large enough to hold the longest returned message. - area length
- Specifies a 4-byte field in your program that contains the length
(in binary) of the area to checkpoint. This parameter is an input
parameter. You can specify up to seven area lengths. For each area
length, you must also specify the area parameter.
All seven area parameters (and corresponding
length parameters) are optional. When you restart the program, IMS restores only the areas you specified
in the
CHKPcall. - area
- Specifies the area in your program that you want IMS to checkpoint. This parameter is an input parameter. You can specify up to seven areas. Each area specified must be preceded by an area length parameter.
Usage
The symbolic CHKP call
commits the changes your program has made to the database and establishes
places in your program from which you can restart your program, if
it terminates abnormally. In addition, the CHKP call:
- Works with the Extended Restart (
XRST) call to restart your program if it terminates abnormally - Enables you to save as many as seven data areas in your program, which are restored when your program is restarted
An XRST call is required before a CHKP call
to indicate to IMS that symbolic
check points are being taken.
Restrictions
The Symbolic CHKP call
is allowed only from batch and BMP applications.