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.