Caching Attributes

Flash Cache Mode

The flashCacheMode attribute is used to display and set the current value for flash cache. The values are writethrough (the default) or writeback. Note the following about the flashCacheMode attribute:

If the attribute is modified from writeback to writethrough and there is existing flash cache, then an error is displayed. The flash cache must be flushed and dropped before changing the attribute to writethrough.
If the attribute is to be modified from writethrough to writeback, then flash cache must be dropped before modifying the attribute.
Write back caching can be disabled on the grid disks that do not need caching, such as the grid disks in the RECO disk group. This allows other objects to use the cache space.
See Also:
- ALTER GRIDDISK for information about disabling caching on grid disks
- Oracle Exadata Database Machine Maintenance Guide for information about enabling and disabling flash cache

Flash Cache Compression

Flash cache compression is first available in Oracle Exadata System Software release 11.2.3.3.0, and only on Oracle Exadata Database Machine X3 and X4 storage servers.

The ALTER CELL flashCacheCompress command enables or disables flash cache compression. The options are true to enable flash cache compression, and false to disable flash cache compression. To enable flash cache compression on Oracle Exadata Database Machine X3 and X4 storage servers, use the following command:

CellCLI> ALTER CELL flashCacheCompress=true

Note:

Oracle Advanced Compression Option is required to enable flash cache compression.
The flashCacheCompress cell attribute is no longer available starting with Oracle Exadata System Software release 24.1.0.

RAM Cache Mode

The ramCacheMode attribute can be set to on, off, or auto. The default value is auto, which means the RAM Cache feature is not enabled. When you modify this attribute, you must restart CELLSRV for the change to take effect.

Note:

Commencing with the September 2022 Oracle Exadata System Software release updates (versions 22.1.3, 21.2.16, and later), the storage server RAM Cache feature is deprecated.