federated_async - Maximum asynchronous TQs per query configuration parameter

Configuration type

Database manager

Applies to

• Partitioned database server with local and remote clients when federation is enabled.

Parameter type

Configurable online

Default [range]

0 [0 to 32 767 inclusive, -1, ANY]

When ANY or -1 is specified, the optimizer determines the number of ATQs for the access plan. The optimizer assigns an ATQ to all eligible SHIP or remote pushdown operators in the plan. The value that is specified for DB2_MAX_ASYNC_REQUESTS_PER_QUERY server option limits the number of asynchronous requests.

Recommendation

The federated_async configuration parameter supplies the default or starting value for the special register and the bind option. You can override the value of this parameter by setting the value of the CURRENT FEDERATED ASYNCHRONY special register, FEDERATED_ASYNCHRONY bind option, or FEDERATED_ASYNCHRONY prepcompile option to a higher or a lower number.

If the special register or the bind option do not override the federated_async configuration parameter, the value of the parameter determines the maximum number of ATQs in the access plan that the federated server allows. If the special register or the bind option overrides this parameter, the value of the special register or the bind option determines the maximum number of ATQs in the plan.

Any changes to the federated_async configuration parameter affect dynamic statements as soon as the current unit of work commits. Subsequent dynamic statements recognize the new value automatically. A restart of the federated database is not needed. Embedded SQL packages are not invalidated nor implicitly rebound when the value of the federated_async configuration parameter changes.

If you want the new value of the federated_async configuration parameter to affect static SQL statements, you need to rebind the package.