5.1.2 Persistent Storage Index

Storage indexes help Oracle Exadata System Software to avoid unnecessary I/O operations. By avoiding unnecessary I/O, affected operations perform better. Also, overall system throughput increases because the saved I/O bandwidth can be used to perform other work.

Oracle Exadata System Software creates and maintains a storage index in shared memory on Exadata Storage Server. For each storage region, the storage index automatically tracks minimum and maximum column values and set membership. Storage index functionality works transparently with no user input. There is no need to create, drop, or tune the storage index.

Starting with Oracle Exadata System Software release 21.2.0, the storage index can persist across cell restarts and upgrades. When the feature is enabled, the storage index shared memory segments are written to the storage server system disks during a graceful shutdown, and these are automatically restored during restart. In the event of a cell server crash or offload server crash, the storage index shared memory segments are retained by the operating system and are immediately available when the software service restarts.

On Oracle Exadata Database Machine X7-2 and later systems with M.2 solid-state drives (SSD), persistence can also be maintained across Oracle Exadata System Software upgrades.

This feature eliminates the need to rebuild the storage index and enables more consistent query performance immediately after a cell restart.

The feature is controlled by setting the storageIndexPersMode cell attribute.

Minimum requirements:

• Oracle Exadata System Software release 21.2.0
• Oracle Database 12c Release 2 (12.2)