1.2.3.1 Exadata Smart Flash Cache

Exadata Smart Flash Cache stores frequently accessed data in high-performance flash storage.

Exadata Smart Flash Cache automatically works in conjunction with Oracle Database to intelligently optimize cache efficiency by favoring frequently accessed and high-value data. Each database I/O contains a tag that indicates the likelihood of repeated data access. This information is combined with internal statistics and other measures, such as the object size and access frequency, to determine whether to cache the data.

Just as importantly, Exadata Smart Flash Cache avoids caching data that will never be reused or will not fit into the cache. For example, a backup operation does not read data repeatedly, so backup-related I/O is not cached.

By default, caching occurs automatically and requires no user or administrator effort.

Although it is generally not required or recommended, Oracle Exadata System Software also enables administrators to override the default caching policy and keep specific table and index segments in or out of the cache.

Originally, Exadata Smart Flash Cache operated exclusively in Write-Through mode. In Write-Through mode, database writes go to disk first and subsequently populate Flash Cache. If a flash device fails with Exadata Smart Flash Cache operating in Write-Through mode, there is no data loss because the data is already on disk.