Types of affinity

Two types of affinity affect dynamic routing; inter-transaction affinity and transaction-system affinity. Inter-transaction affinity occurs among a set of transactions that share a common resource or coordinate their processing. Transaction-system affinity is an affinity between a transaction and a particular CICS region, where the transaction interrogates or changes the properties of that CICS region.

Inter-transaction affinity

Transaction affinity among two or more CICS® transactions is caused by the transactions using techniques to pass information between one another, or to synchronize activity between one another, in a way that requires the transactions to execute in the same CICS region.

This type of affinity can occur in the following circumstances:

One transaction terminates, leaving 'state data' in a place that a second transaction can only access by running in the same CICS region as the first transaction.
One transaction creates data that a second transaction accesses while the first transaction is still running. For this to work safely, the first transaction typically waits on some event, which the second transaction posts when it has read the data created by the first transaction. This technique requires that both transactions are routed to the same CICS region.
Two transactions synchronize, using an event control block (ECB) mechanism. Because CICS has no function shipping support for this technique, this type of affinity means that the two transactions must be routed to the same CICS region.
Note: The same is true if two transactions synchronize, using an enqueue (ENQ) mechanism, unless you have used appropriate ENQMODEL resource definitions to give sysplex-wide scope to the ENQs. See ENQMODEL resource definitions .

Transaction-system affinity

Transactions with affinity to a particular system, rather than another transaction, are not eligible for dynamic routing. In general, they are transactions that use INQUIRE and SET commands, or have some dependency on global user exit programs, which also have an affinity with a particular CICS region.

Using INQUIRE and SET commands and global user exits

There is no remote (that is, function shipping) support for INQUIRE and SET commands, nor is there a SYSID option on them, hence transactions using these commands must be routed to the CICS regions that own the resources to which they refer. In general, such transactions cannot be dynamically routed to any target region, and therefore transactions that use INQUIRE and SET should be statically routed.

Global user exits running in different CICS regions cannot exchange data. It is unlikely that user transactions pass data or parameters with user exits, but if such transactions do exist, they must run in the same target region as the global user exits.

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Last updated: Thursday, 27 June 2019