Indexes in parallel

If you specify more than one index, CHECK INDEX checks the indexes in parallel unless they are constrained by available memory, sort work files, or the PARALLEL option. Sorting the index keys and checking multiple indexes in parallel, rather than sequentially, reduces the elapsed time for a CHECK INDEX job.

If you do not specify the PARALLEL option, the PARAMDEG_UTIL subsystem parameter determines the maximum degree of parallelism for the utility.

The following figure shows the flow of a CHECK INDEX job with a parallel index check for a nonpartitioned table space or a single partition of a partitioned table space.

Figure 1. Parallel index check for a nonpartitioned table space or a single partition of a partitioned table space
Begin figure summary. CHECK INDEX unloads the table space singularly, then sorts the index keys and checks multiple indexes in parallel. Detailed description available.

The following figure shows the flow of a CHECK INDEX job with a parallel index check for all partitioning indexes on a partitioned table space.

Figure 2. Parallel index check for all partitioning indexes on a partitioned table space
Begin figure summary. CHECK INDEX unloads multiple table space parts, then sorts the index keys and checks the index parts in parallel. Detailed description available.

The following figure shows the flow of a CHECK INDEX job with a parallel index check for a partitioned table space with a single nonpartitioned secondary index.

Figure 3. Parallel index check for a partitioned table space with a single nonpartitioned secondary index
Begin figure summary. CHECK INDEX unloads multiple table space parts and sorts the index keys in parallel, then merges and checks the index. Detailed description available.

The following figure shows the flow of a CHECK INDEX job with a parallel index check for all indexes on a partitioned table space. Each unload task pipes keys to each sort task, sorting the keys and piping them back to the check tasks.

Figure 4. Parallel index check for all indexes on a partitioned table space
Begin figure summary. CHECK INDEX concurrently unloads multiple table space parts, sorts index keys, and check indexes. Detailed description available.