Administration of the PMA Server › Technical Overview › User Exits › General Operation

General Operation

All user exits of the Server operate in a similar way for best performance and security.

• The created name/token from the Server is retrieved to get the linkage information for the cross-memory environment. When this name/token cannot be found, the user exit returns to the caller immediately.
• The user exit connects to the Server address space and calls the proper service routine with a PC (Program call) instruction.
• After the Server service routine has returned control to the user exit, the connection to the Server address space is released.

All user exits return with a return code of zero to the caller. Thus, any KEEPRC specifications (either statically or dynamically) for other user exits of the same exit point in the system are not affected.

The above description determines that a user exit only has connection to the Server address space for the processing of a single event, not across multiple user exit calls by the system. This limitation is for safety aspects. Whenever the Server terminates for some reason (cancel or abend), the created name/token for the linkage information is deleted by the system and is no longer available for the user exits upon the next invocation. In this case, the uses exits do nothing, even if they might still be activated. Also, it is possible to register the Server user exits in the PROGxx member of the SYS1.PARMLIB statically with an active state at IPL time. As long as the Server has not come up and the name token for the linkage is not present, the user exits effectively do nothing.