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Online reorganization

The following topics discuss online reorganizations in-depth, concentrating on the aspects of reorganization processing that are unique to SHRLEVEL CHANGE. Aspects that are the same as those for other types of reorganizations are covered in other topics in this space.

Related topic

Operational-considerations

Performing an online reorganization by specifying SHRLEVEL CHANGE on the REORG command offers the following benefits:

  • Allows full access to Db2 data during most of the reorganization
  • Delivers improved data availability by greatly reducing the outage for the Db2 objects, thus helping to meet growing 24 x 7 requirements
  • Operates in a nondestructive manner, allowing you to make the objects available without having to recover in the event of a failure

  • Optionally provides support for batch applications that use the BMC APPLICATION RESTART Control (AR/CTL) product

    Online reorganizations use the AR/CTL suspend-and-resume interface, which eliminates the outage for Db2 objects.

Important

To use the SHRLEVEL CHANGE option, you must have installed the BMC SNAPSHOT UPGRADE FEATURE (SUF) (also known as XBM).

An online reorganization allows read-write (RW) application access to Db2 table space and index space objects during most of the reorganization process.

To invoke an online reorganization, REORG PLUS provides the SHRLEVEL CHANGE keyword. When you specify SHRLEVEL CHANGE, REORG PLUS performs the following processing steps after the utility initializes:

  1. (optional) Analyzes the original Db2 table space and index space objects
  2. Externalizes changed pages for the original table space and index space objects and starts capturing log records
  3. Unloads table space or index space data from the original Db2 objects by using the SUF (also known as  XBM) product or its technology
  4. Allocates staging objects that mirror the original table space or index space objects, or uses predefined staging objects
  5. Reloads data into the staging table space objects, and builds or updates the staging index space objects
  6. Creates a row ID (RID) translation map for a table space reorganization

  7. Applies log records to the staging objects to reflect all update activity since SUF (also known as XBM) was initialized

    REORG PLUS uses the RID translation map to reconcile the log records for a table space reorganization.

  8. Prevents any access to the original objects and switches the data sets, which causes the staging objects to replace the original objects
  9. Registers full and incremental copies, ensuring the recoverability of objects
  10. Allows full access to the objects to resume
  11. Optionally updates the Db2 catalog and DASD MANAGER PLUS statistics tables

The following figure illustrates the processing flow for a SHRLEVEL CHANGE reorganization:

processing_flow_SHRLEVEL_CHANGE.png

 

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