Enabling parallel processing for column-organized tables

Certain operations on column-organized tables such as access and query processing, require enabling of intraquery parallelism and intrapartition parallelism.

Before you begin

  • You must have the proper authorization to configure instances and databases.

About this task

The processing of queries against column-organized tables require that intraquery parallelism be enabled for the application that is compiling and executing the query. The following statement types also require intraquery parallelism:
  • All DML operations that reference column-organized tables
  • The ALTER TABLE ADD UNIQUE / PRIMARY KEY CONSTRAINT statement against a column-organized table if rows were inserted into the table
  • The RUNSTATS command against a column-organized table
  • The LOAD command against a column-organized table
If an application attempts to run one of these statements or commands without intraquery parallelism enabled, an error is returned. Intraquery parallelism uses either intrapartition parallelism, interpartition parallelism, or both.

Access to column-organized tables also require intrapartition parallelism. Setting DB2_WORKLOAD to ANALYTICS implicitly enables intrapartition parallelism for workload objects that are created with MAXIMUM DEGREE set to DEFAULT, and is recommended when you use column-organized tables. If this registry variable is not set, or is set to another value, you must explicitly enable intrapartition parallelism before you access column-organized.

Procedure

To enable parallel processing for column-organized tables:

  1. Enable intrapartition parallelism, which in turn enables intraquery parallelism.
    For more information, see Enabling intrapartition parallelism for queries.
  2. Ensure that the shared sort heap is allocated as parallel processing of queries requires use of the shared sort heap.
    Any of the following actions ensure that the shared sort heap is allocated:
    • Set the intra_parallel database manager configuration parameter to YES.
    • Set the sheapthres database manager configuration parameter to 0.
    • Activate the connection concentrator. For more information, see Connection concentrator.