9.1.1 In-Memory Columnar Caching on Storage Servers
Oracle Exadata System Software release 12.2.1.1.0 can use fast vector-processing in-memory algorithms on data in the storage flash cache. This feature is available if you have licensed the Oracle Database In-Memory (Database In-Memory) option.
Oracle Exadata System Software release 12.1.2.1.0 added a columnar flash cache format which automatically stored Exadata Hybrid Columnar Compression data in pure columnar Exadata Hybrid Columnar Compression format in the flash cache. This release extends support for Exadata Hybrid Columnar Compression data to enable the cached data to be rewritten into Database In-Memory format and enabling ultra-fast single instruction, multiple data (SIMD) predicates to be used in Smart Scan. With this format, most in-memory performance enhancements are supported in Smart Scan including joins and aggregation.
Data from normal (unencrypted) as well as encrypted tablespaces can be cached in the in-memory columnar cache format.
Just as with Oracle Database In-Memory, the new Database In-Memory format is created by a background process so that it does not interfere with the performance of queries.
This feature is enabled by default when the INMEMORY_SIZE database initialization parameter is configured and the user does not need to do anything to get this enhancement. See INMEMORY_CLAUSE_DEFAULT in Oracle Database
Reference for information about INMEMORY_SIZE. If INMEMORY_SIZE is not configured, then the Exadata Hybrid Columnar Compression format columnar cache is still used exactly as in 12.1.2.1.0.
If you need to disable this feature, you can use a new DDL keyword CELLMEMORY with the ALTER TABLE command. See Enabling or Disabling In-Memory Columnar Caching on Storage Servers in Oracle Exadata System Software User's Guide.
Minimum requirements:
- Oracle Database 12c release 1 (12.1.0.2), minimum software version required is 12.1.0.2.161018DBBP or
- Oracle Database 12c release 2 (12.2.0.1)
- Patch for bug 24521608