WARNING!
Any failure in a JES2 Exit may result in an unstable or potentially unusable system.
Please use extreme caution when modifying, removing or reinstalling any JES exits.
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JES2 Exits
We would be very neglectful if on this page we didn't issue a warning about JES exits.
JES exits have the potential to make your operating system useless so extreme caution should be exercised before implementing new JES exits or recoding old JES exits.
If possible always use a sandbox system for the testing of your JES exits and use dynamic activation and deactivation of the exits on a quiesced system.
Activating/Deactivating
Many (but not all) of the exits can be activated or deactivated 'inflight' and there are basically two ways of activating and deactivating a JES exit, only one of these is a permanent activation (across JES2 restarts).
Exits that create token pairs can not be temporarily deactivated, these should be placed in (or removed from) the JES2 initialization deck and JES2 restarted in order to activate or deactivate them. It is strongly recommended that any changes to these token pair exits are changed via an IPL as the tokens can survive a JES2 hot restart.
Permanent Activation
Permanent activation or deactivation is achieved by way of adding or altering the LOADMOD and EXIT statements in the JES2 Initialization deck and then IPLing the system. The LOADMOD and EXIT(nn) statements must come before any new statements using any keywords supported in the exits themselves. This is why the recommendation is made that new initialization statements are placed at the very bottom of the initialization deck.
The format of the LOADMOD and EXIT(nn) statements is documented in the IBM documentation and will not be covered in this document other than in the portion of the document that describes the current JES2 Initialization implementation for all of the exits described in this document.
Temporary Activation
Temporary activation or deactivation is achieved by using the $TEXIT and the $ADD or $DEL JES2 commands.
These commands will only work if the JES2 subsystem is already active. These commands are ineffective if the exits themselves are already called. In other words if an exit goes into a loop issuing the command to deactivate the exit will not break out of the loop for you. Under these conditions an IPL is usually the only way out of the loop.
In order to deactivate and remove an exit issue the following commands:
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$TEXIT(nn),ROUTINES=(-EXITnnC) $DEL LOADMOD(BSLJXnnB) |
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To activate (or reactivate) use: |
$ADD LOADMOD(BSLJXnnB) $TEXIT(nn),ROUTINES=(+EXITnnC) |
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Note : It should be noted that there are several exits that require a slightly different $ADD command as they reside in CSA and so the $ADD command for these would be: |
| $ADD LOADMOD(BSLJX50B),STORAGE=CSA |
