5.1.3 Persistent Columnar Cache

The columnar cache is a portion of Exadata Smart Flash Cache that contains data in columnar format. Data in Exadata Smart Flash Cache is automatically converted to columnar format and stored in the columnar cache to aid query performance.

Before Oracle Exadata System Software release 21.2.0, metadata for managing the columnar cache is lost when the cell fails or shuts down. Consequently, the columnar cache must be rebuilt following each cell restart.

Starting with Oracle Exadata System Software release 21.2.0, the columnar cache can persist across cell restarts and upgrades. This feature saves resources associated with rebuilding the cache and enables more consistent query performance immediately after a cell restart.

To use persistent columnar cache, Exadata Smart Flash Cache must be in Write-Back mode. The feature is controlled by setting the columnarCachePersMode cell attribute.

Minimum requirements:

• Oracle Exadata System Software release 21.2.0