If the JRNAD is taken for I/O errors, a journal exit can zero out, or otherwise alter, the physical-error return code, so that a series of operations can continue to completion, even though one or more of the operations failed.

The contents of the parameter list built by VSAM, pointed to by register 1, can be examined by the JRNAD exit routine, which is described in Table 1.

If the exit routine issues GENCB, MODCB, SHOWCB, or TESTCB, it must restore register 14, which is used by these macros, before it returns to VSAM.

If the exit routine uses register 1, it must restore it with the parameter list address before returning to VSAM. (The routine must return for completion of the request that caused VSAM to exit.)

The JRNAD exit must be indicated as active before the data set for which the exit is to be used is opened, and the exit must not be made inactive during processing. If you define more than one access method control block for a data set and want to have a JRNAD routine, the first ACB you open for the data set must specify the exit list that identifies the routine.

When the data set being processed is extended addressable, the JRNAD exits dealing with RBAs are not taken or are restricted due to the increase in the size of the field required to provide addressability to RBAs which may be greater than 4 GB. The restrictions are for the entire data set without regard to the specific RBA value.