Rebuild access paths

Rebuilding a database access path might take as much as one minute for every 10 000 records. But some factors might affect the time estimate for rebuilding access paths.

The following factors affect the time estimate for rebuilding access paths:

• Storage pool size. You can improve the rebuild time by running the job in a larger storage pool.
• The system model. The speed of the processing unit is a key factor.
• Key length. A large key length slows rebuilding the access path because the access path constructs and stores more key information.
• Select/omit values. Select/omit processing slows the rebuilding of an access path because the system compares each record to see if it meets the select/omit values.
• Record length. A large record length slows the rebuilding of an access path because the system looks at more data.
• Storage device that contains the data. The relative speed of the storage device that contains the actual data and the device that stores the access path affects the time needed to rebuild an access path.
• The order of the records in the file. The system tries to rebuild an access path so that it can find information quickly when using that access path. The order of the records in a file has a small affect on how fast the system builds the access path while trying to maintain an efficient access path.

• Control when access paths are rebuilt
  If the system ends abnormally, during the next initial program load (IPL), the system automatically lists those files that require access path recovery. You can control when access paths are rebuilt.
• Design files to reduce access path rebuilding time
  File design can help reduce access path recovery time.
• Other methods to avoid rebuilding access paths
  If you do not journal your access paths or do not take advantage of system-managed access-path protection (SMAPP), consider other system functions that reduce the chances of rebuilding access paths.