Dynamic PER traps

TARGETID, along with indirect addressing on the RANGE parameter, allows you to activate a new PER trap dynamically once the previous trap has been deactivated as a result of MATCHLIM. In the next example, specifying TARGETID=TR2 on the first PER trap will cause the second PER trap, ID=TR2, to activate when the first trap deactivates. The address range of the second PER trap is determined by the contents of register 1 when the MATCHLIM occurs.

   First PER trap:

        SLIP SET,IF,RANGE=10000,TARGETID=TR2,ACTION=TARGETID,END

   Second PER trap:

        SLIP SET,SA,DISABLE,RANGE=1R?,ID=TR2,ACTION=SVCD,END

The second PER trap can specify a third trap and so on. There is no limit to the number of traps in a chain of dynamic traps, which is called a dynamic PER activation chain.

Each PER trap can be of any kind and have its own unique set of matching criteria or filters. However, PER traps will be active only for address spaces specified in the initial trap by the JOBNAME, ASID, and MODE=HOME parameters. Therefore IBM® recommends that an ASID parameter specified in the initial trap must include all address spaces for the subsequent traps. For example, it makes sense to specify ASID=(1,2,3) on the initial trap and ASID=(1,2) on the second trap, but not the reverse, because no units of work would be monitored in ASID=3.

Rules for dynamic PER traps:

TARGETID can be used with all PER traps except IGNORE.
When TARGETID is one of the parameters, you must also specify it as one of the actions. Otherwise the TARGETID parameter will be ignored.
Each of the PER traps can have its own independent action.
When TARGETID is specified the default value for MATCHLIM is 1.
The RANGE parameter on all PER traps support indirect addressing.
A dynamic PER activation chain is defined when every TARGETID can be associated with some PER trap. SLIP does not allow the traps of the chain to be enabled unless the definition is complete.
- A PER trap within a dynamic PER activation chain cannot target itself or a preceding trap in the chain. In other words, a dynamic PER activation chain cannot be a circular chain.
- Members of the chain cannot be deleted. Any attempt to delete a member will result in message IEE408I being issued.
- You can disable any trap in the chain in order to delete the chain. This can aid in tracking down the currently active trap.
SLIP allows specification of NUCMOD, PVTMOD, and LPAMOD on the trap. However for PVTMOD, the cross memory lock (CML) of the primary address space that existed at the time of the PER interrupt must be immediately obtainable in order to search for the specified load module. If the CML is obtainable but the system does not find the specified load module, it puts the target trap into an enabled but inactive state.