Using the XRST call

Use the XRST call to invoke AR/CTL checkpoint/restart support and to enable AR/CTL data services. This call results in a normal start, cold start, or restart environment, depending on the AR/CTL restart determination routines.


If an application program uses checkpoint/restart support or any AR/CTL data services, it must issue the restart call once as the first call and before any data set open processing.

When the application program issues the XRST call, AR/CTL repositions the database and GSAM files. If the application program is using DB2 but does not use the Automatic DB2 Cursor Repositioning processing option, the application program must reposition the DB2 tables by using the key information in a data area saved in the CHKP call.


The XRST call must specify user areas identical to those specified in the CHKP calls.

Call format

The following example shows the XRST call in COBOL:

CALL 'CBLTDLI' USING XRST, chkppcb, chkplen, chkparea,
     userlen-1, userarea-1, userlen-n, userarea-n
Call Parameters

The following parameters are valid on the XRST call


Required. The checkpoint PCB. This PCB is defined in the ASB.


Required. The address of any four-byte area in the program. AR/CTL does not use this area, but a value is required for compatibility with IMS.


Required. The name of the 8-byte checkpoint I/O area. For information about how to define this area in the application program, see Coding the checkpoint I/O area.


At least one user area is required in an IMS compatible environment (where IMS is not present during the execution). It is not necessary for any user area to begin or end on a fullword boundary.


Required. The name of a 4-byte field that contains the binary length of the first application program data area to restore. These values must define areas that were saved during checkpoint processing.


If a user area length is specified incorrectly, results will be unpredictable.


Required. The name of the first data area to save in the checkpoint record. It is usually a structure name.

userlen-n, userarea-n

Optional. The address of the length and the name of the next data area to save in the checkpoint record. Provide a pair of userlen-n and userarea-n parameters for each defined data area you want to restore. You can identify a maximum of seven data areas.

Status codes

AR/CTL does not issue any status codes for this call.


After the XRST call, the application program should check any ASAM PCBs for proper status codes. AR/CTL places the status codes associated with opening/repositioning ASAM data sets in the PCB for that data set.

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