Selecting an ILDS update method

You can update the ILDS by using one of three possible methods when you load the logically related databases.

The option that you choose impacts the performance of the load process. Because loading logically related databases takes much longer than it does for other databases, the option that you choose might have a considerable impact on performance.

Use one of the following methods to update your ILDS:

  • To update the ILDS as each logical parent of a unidirectional relationship is loaded or as each logical child of a bidirectional relationship is loaded into the database by the HD Reorganization Reload utility (DFSURGL0), do not specify an ILDS control statement when you run the HD Reorganization Reload utility. This method is the most time consuming.
  • To have the HD Reorganization Reload utility update the ILDS after the logically related database has been reloaded, specify the ILDSMULTI control statement when you run the HD Reorganization Reload utility. This process uses a multi-threaded update process, which can be much more efficient than updating the entries as the target segments are loaded for the following reasons:
    • The writes of the ILDS entries to different partitions are overlapped
    • The writes are sequential
    • The writes are done in load mode, which avoids the overhead of CI and CA splits
    Additionally, you can create free space. Future reorganizations might benefit from having this free space for their updates to the ILDSs.

    The ILDSMULTI control statement is valid only when converting a database to HALDB.

  • To update the ILDS by a means other than the HD Reorganization Reload utility after the logically related databases have been reloaded, specify the NOILDS control statement. If you choose this option, you can use the HALDB Index/ILDS Rebuild utility (DFSPREC0) to update the ILDS.

    Using the NOILDS control statement provides the fastest reload, and the HALDB Index/ILDS Rebuild utility can update the ILDS for each partition in parallel; however, the HALDB Index/ILDS Rebuild utility reads each partition to update its ILDS. Optionally, the HALDB Index/ILDS Rebuild utility can rebuild the ILDS in VSAM load mode, which can improve performance and includes free space in the ILDS.

    You can also use the NOILDS control statement with the HD Reorganization Reload utility when reorganizing an existing HALDB database.