With CICS/ESA 4.1 and later, CICSPlex® SM can evaluate both the health and activity (or
load) of each target region identified by the Target Scope. This information,
along with the abend probability values you provide when defining transaction
groups to CICSPlex SM, is then used in determining to which target region a particular
transaction should be routed. That is, it is used as a guide to avoiding target regions
where the abend probability is greater than is acceptable for a given transaction
or set of transactions within the transaction group.
Note:
For any transactions that are not associated with a transaction
group, the default abend probability values defined in the workload specification
are used.
The probability that a transaction will abend if routed to a particular target region
is calculated in one of the following ways:
- When the transaction is associated with a transaction group that either
has no defined affinity type and lifetime or uses the default values defined
in a workload specification, then the probability of an abend is calculated individually
for that transaction.
- When the transaction is associated with a transaction group that has a
defined affinity type and lifetime, then the probability of an abend for that
transaction is calculated as the probability of an abend for the entire group
of transactions.
The abend probability values that you provide cover both the health and
load of a potential target region, where:
- If the probability that a given transaction within the set will abend
in a specific target region is equal to or greater than the abend health value
you specified with the transaction, then that target region is considered unhealthy. CICSPlex SM
attempts to avoid routing the transaction to that target region. However, if there
is no healthier target region, then the transaction may be routed to that target region.
- If the probability that a given transaction within the set will abend
in a specific target region is greater than 0% but less than the abend
load value you specified, CICSPlex SM gradually adjusts the perceived transaction
load upward. Once the abend probability reaches the defined load value, the
perceived load is doubled, which means the target region is considered to have
twice the load that it really has. The target region is still considered healthy,
but its perceived load may make it less acceptable as a target for routing.
The perceived load continues to increase until the abend probability reaches
the defined health value, at which point the target region is considered unhealthy.
Notes:
- Once an affinity is active, all subsequent transactions are routed to
the same target region for as long as the affinity remains active, regardless of
its abend probability.
- If a transaction abends in a target region with EXEC CICS HANDLE ABEND
in force, CICSPlex SM does not receive the information that the abend has
occurred. Therefore, CICSPlex SM cannot take such abends into account when
calculating the probability that a transaction will abend in that target region.
In other words, the abend probability might stay low in this situation, even
though abends had occurred.
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