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CURRENT QUERY ACCELERATION WAITFORDATA special register

The CURRENT QUERY ACCELERATION WAITFORDATA special register specifies the maximum amount of time, if any, that the accelerator delays a dynamic SQL query while the accelerator waits for the replication of committed Db2 data changes that occurred prior to Db2 running the query. This special register does not apply to static SQL queries.

The data type is a DECIMAL(5,1) in the form of nnnn.m.

Valid values are a numeric constant in the range of 0.0–3600.0 seconds. For example, a value of 20.0 represents 20.0 seconds (or 20000 milliseconds), and a value of 30.5 represents 30.5 seconds (or 30500 milliseconds). The maximum value of 3600.0 means that the query is delayed for 60 minutes.

The default value is 0.0, which means that the query is not delayed and is run immediately on the accelerator. Other WAITFORDATA behavior is not applied to the query.

The wait time value can also be specified as an INTEGER numeric constant value ranging from 0 - 3600 seconds, which Db2 will convert to a DECIMAL (5,1) value.

You can change the value of the special register by executing the SET CURRENT QUERY ACCELERATION WAITFORDATA statement.

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The initial value of CURRENT QUERY ACCELERATION WAITFORDATA is determined by one of the following settings:
  • The value of Db2 QUERY_ACCEL_WAITFORDATA subsystem parameter. The default for the initial value of this subsystem parameter is 0.0 unless your installation has changed the value.
  • If specified for the bind of a package, the ACCELERATIONWAITFORDATA bind option. This behavior enables the ACCELERATIONWAITFORDATA bind option to be used to specify the acceleration behavior for both dynamic SQL queries and static SQL queries. This bind option does not have a default value.

The initial value of CURRENT QUERY ACCELERATION WAITFORDATA in a user-defined function or stored procedure is inherited according to the rules in Special registers in a user-defined function or a stored procedure.

You can change the value of the register by executing the SET CURRENT QUERY ACCELERATION WAITFORDATA statement.

The precedence order (lowest to highest) for setting the value of the special register is as follows:
  • The QUERY_ACCEL_WAITFORDATA subsystem parameter
  • The ACCELERATIONWAITFORDATA bind option, if specified
  • An explicit SET CURRENT QUERY ACCELERATION WAITFORDATA statement
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For more information about the restrictions, requirements, and behaviors associated with CURRENT QUERY ACCELERATION WAITFORDATA, see SET CURRENT QUERY ACCELERATION WAITFORDATA statement.

Example: The following statement sets the CURRENT QUERY ACCELERATION WAITFORDATA special register so that the accelerator delays queries for 180 seconds (three minutes) while it waits for committed Db2 data changes to be replicated to the accelerator.
  SET CURRENT QUERY ACCELERATION WAITFORDATA 180;
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