Db2 batch connections and allied threads

While it is executing, CDC Replication opens several DB2® plans under separate sub-tasks. Each DB2 plan is opened using the DB2 batch Call Attach Facility, and so each opened DB2 plan requires a DB2 batch connection and represents a DB2 user.

Running CDC Replication may require an adjustment to the maximum number of batch connections and allied threads (users) that DB2 can support. In order to determine what these adjustments (if any) are, you will need to know the maximum number of open plans that CDC Replication will require. CDC Replication keeps its DB2 plans open only as long as they are required, and closes them as soon as they are no longer needed. Accordingly, you will need to know the maximum number of concurrent replication and support activities that can be ongoing at one time.

The following list is a set of guidelines to help you determine the number of allied threads CDC Replication will require, once you know how many concurrently active replication and support activities you plan to use:

  • When CDC Replication starts, it opens one DB2 plan.
  • If the Log Cache is configured, CDC Replication opens one additional DB2 plan.
  • For each agent that is connected, and for the duration of that connection, CDC Replication opens one DB2 plan.
  • For each ongoing describe (describes are usually very quick), CDC Replication opens two DB2 plans. The first plan is closed shortly after the second plan is opened. This is true whether CDC Replication is the transmitter or receiver of the described data.
  • For each source subscription that is refreshing a table, CDC Replication opens two DB2 plans. The first plan is closed shortly after the second plan is opened.
  • For each source subscription that is mirroring a table, CDC Replication opens two DB2 plans. The first plan is closed shortly after the second plan is opened but is briefly reopened when the subscription is shutting down
  • For each target subscription that is receiving table changes from a source environment refresh or mirror activity, CDC Replication opens two plans. The first plan is closed shortly after the second plan is opened, but is briefly reopened each time the source resets the bookmark during mirroring, if ever.