Update-mode JQA considerations

If an exit requires an update-mode JQA, use the following logic path:

Perform the action:
```
$DOGJQE ACTION=(FETCH,UPDATE),JQE=jqe, WAIT=NO 
```
where jqe is the address of the JQE that the IBM® code gives to the exit.
If JES2 returns a return code indicating that the JQA could not be created, you must manage the situation of lock not available.
If RC=0, perform rest of logic by using the JQA.
Perform the action:
```
$DOGJQE ACTION=RETURN,CBADDR=jqa
```
where jqa is the address that is returned in R0 from FETCH in the first step.

Note: It is not necessary or desirable to perform the following action before you attempt to get an update-mode JQA.

$DOGJQE ACTION=(QUERYLOCK,OBTAINABLE)

This is valid because the non-zero return code (that is, the failure RC) returned by QUERYLOCK indicates that the lock is not available for a new user. This condition is different from requesting an update-mode JQA for the current caller.