2.1.4 Flash Cache Size Advisor

Oracle Exadata System Software release 26.2.0 introduces Flash Cache Size Advisor. The advisor provides recommendations to help administrators use flash cache capacity efficiently and optimize I/O performance.

The advisor runs on the Exadata storage servers, where it analyzes workload I/O activity over time and automatically generates recommendations for refining Exadata Smart Flash Cache allocations. Advisory information from multiple storage servers is collected in the Oracle AI Database Automatic Workload Repository (AWR), and recommendations are aggregated and delivered through the Automatic Database Diagnostic Monitor (ADDM) framework.

You can view advisor recommendations in ADDM reports or in the ADDM section of AWR reports. You can retrieve ADDM reports by using the DBMS_ADDM package APIs, or view them using an ADDM client such as Oracle Enterprise Manager.

For environments that use Exadata I/O Resource Management (IORM) to manage flash cache allocations for individual databases, the advisor can recommend targeted allocation increases for specific databases. For environments that do not limit flash cache resources for individual databases, the advisor can recommend adding storage servers to increase overall flash cache capacity if workload analysis indicates that more capacity is needed.

Each recommendation includes an estimated benefit and a summary of its rationale. For example:

Finding 1: Exadata Flash Cache Advisory
Impact is 503.57 active sessions, 81.89% of total activity.
-----------------------------------------------------------
The Exadata flash cache size was insufficient for the workload.

   Recommendation 1: Exadata Configuration
   Estimated benefit is 503.57 active sessions, 81.89% of total activity.
   ----------------------------------------------------------------------
   Action
      Consider increasing the flash cache size for CDB CDB1 by 52.06 GB.
      This adjustment is projected to improve flash cache hit rates up to:
      small reads: 25.5%, small writes: 94.96%, large reads: 5.98%, large
      writes: 65.54%.
   Rationale
      The overall disk IO latency for CDB CDB1 was 3028.16 ms, with hard
      disk activity accounting for 38 IOPs per device (74.55% of the total
      IOPs) over 6 storage cells.

   Symptoms That Led to the Finding:
   ---------------------------------
      Wait class "User I/O" was consuming significant database time.
      Impact is 503.57 active sessions, 81.89% of total activity.

Administrators can use ongoing analysis to evaluate the impact of changes and align flash cache capacity with changing workload requirements.

Flash Cache Size Advisor works in conjunction with Oracle AI Database version 23.26.4 (October 2026 Release Update) or later.