JOA processing considerations

When your exit returns a JOA to the JES2 systems through these actions, certain errors can occur if JES2 determines that what your exit has returned is not consistent with what JES2 knows to exist. JES2 uses the $ERROR macro and issues the following errors:

D01– Non-IBM code returned an IBM JOE or JOA that violates the consistency checks of JES2.
D02– IBM code returned a non-IBM JOE or JOA that violates the consistency checks of JES2.

Note:

You are encouraged to disregard the kind of JOA that is passed to your exit and always to do the following actions:
- To obtain the address of a read–mode JOA (for example, your exit needs to examine but not change the JOEFORM field), perform the action:
```
$DOGJOE ACTION=(FETCH,READ)
```
- To obtain the address of an update–mode JOA (for example, your exit needs to change the JOEHSRSN field), perform the action:
```
$DOGJOE ACTION=(FETCH,UPDATE)
```
If you are writing JES2 exits that are in the following situations:
- Run outside the JES2 main task
- Need to access or update checkpoint control blocks
you need to follow the specific coding recommendations in Checkpoint control blocks and those specific "Programming Considerations" listed for the JES2 exit that you are implementing.