1. Database Administrator's Guide for Oracle Essbase
  2. Optimizing Database Restructuring
  3. Actions That Improve Performance

Actions That Improve Performance

Several actions improve performance related to database restructuring:

  • If you change a dimension frequently, make it sparse.

  • Use incremental restructuring to control when Essbase performs a required database restructuring.

  • Consider using parallel restructuring on multiprocessor systems.

  • Select options when you save a modified outline that reduce the amount of restructuring required.

Parallel Restructuring

By default, block storage restructuring is performed sequentially. Blocks are renumbered and reshaped from first to last, a time-intensive process. Parallel restructuring can reduce restructuring time by dividing block restructuring work across multiple concurrent threads to use available processor cores. Because calculation is performed separately from restructuring, each block can be restructured independently of other blocks.

Blocks are divided into n groups, where n is the number of restructuring threads. This division is performed by traversing the breadth of the index BTree until the number of keys at a level is equal to or greater than n. If there is no level with more than n keys, the number of restructuring threads is reduced accordingly.

The number of restructuring threads to use is defined using the RESTRUCTURETHREADS configuration setting. If RESTRUCTURETHREADS is not defined, the default is one thread.

Options for Saving a Modified Outline

Essbase displays a dialog box when you save outline changes that trigger database restructuring (using Outline Editor). In the Restructure Database dialog box, you define how data values are handled during restructure; for example, you can preserve all data, preserve only level 0 or input data, or discard all data during restructure.

If the database contains data, you need enough free disk space on the server to create a backup copy of the database. Backup ensures that any abnormal termination during the restructure process does not corrupt the database.

Essbase may display a message that restructuring is not required, yet still perform an index-only restructure. This event most likely occurs if you make changes to a sparse dimension. If you try to cancel a restructure operation, Essbase may issue a message indicating that the operation cannot be canceled. If such a message is displayed, Essbase is performing final cleanup, and it is too late to cancel.