Oracle Database In-Memory concepts in 19c

Version 19.8 has below updates:

New Features

The following major features are new in this release.

  • Database In-Memory Base LevelStarting with Oracle Database release 19c, version 19.8, you can enable the Database In-Memory Base Level by setting the INMEMORY_FORCE initialization parameter to BASE_LEVEL. The Base Level enables you to experiment with In-Memory features without purchasing the Oracle Database In-Memory option.When the Base Level is enabled, the IM column store size is limited to 16 GB for a CDB or non-CDB and for every database instance in an Oracle RAC database. Also, the compression level for all objects and columns is set to QUERY LOW automatically and transparently, and Automatic In-Memory is disabled. The CELLMEMORY feature is disabled for Oracle Exadata.
  • Starting with Oracle Database release 19c, version 19.8, you can use the CellMemory feature without enabling the IM column store by setting INMEMORY_FORCE=CELLMEMORY_LEVEL and INMEMORY_SIZE=0. With these settings, the IM column store is not enabled and queries can use CellMemory to scan objects.In previous releases of Oracle Database, in order to use the CellMemory feature, you were required to enable the IM column store, even if you had no intention of using it. This incurred the overhead of enabling the IM column store without any benefit.

 

Changes in Oracle Database Release 19c, Version 19.1

New Features

  • Database In-Memory Base LevelEnable the Database In-Memory Base Level by setting the INMEMORY_FORCE initialization parameter to BASE_LEVEL. The Base Level enables you to experiment with In-Memory features without purchasing the Oracle Database In-Memory option.When the Base Level is enabled, the IM column store size is limited to 16 GB for a CDB or non-CDB and for every database instance in an Oracle RAC database. Also, the compression level for all objects and columns is set to QUERY LOW automatically and transparently, and Automatic In-Memory is disabled. The CELLMEMORY feature is disabled for Oracle Exadata.
  • Database In-Memory wait on populateThe DBMS_INMEMORY_ADMIN.POPULATE_WAIT function initiates population of all INMEMORY objects that have a priority greater than or equal to the specified priority, and returns a status value for the population. A user-specified interval specifies the maximum time that the function waits before returning the value to the caller.
    • The ORACLE_HIVE and ORACLE_BIGDATA drivers are supported.
    • Parallel query is supported.
    • A full table scan populates an In-Memory external table. In previous releases, population required using the POPULATE or REPOPULATE procedure of DBMS_INMEMORY.
    • The In-Memory background processes, rather than a foreground process, now drop IM segments.Big Data and performance enhancements for In-Memory external tablesThis release introduces several manageability and performance improvements to the In-Memory external tables feature:
  • Hybrid partitioned tablesPartitions can reside in both Oracle Database segments and in external files and sources. This feature significantly enhances partitioning for Big Data SQL, where large portions of a table can reside in external partitions. Only the internal partitions of a hybrid partitioned table inherit the INMEMORY attribute.
  • Oracle Database Resource Manager automatically enabled for Database In-MemoryWhen INMEMORY_SIZE is greater than 0, the Resource Manager is automatically enabled.
  • Oracle Data Guard Multi-Instance Redo Apply supports the IM column storeSetting the initialization parameter ENABLE_IMC_WITH_MIRA to TRUE enables the IM column store and Data Guard Multi-Instance Redo Apply at the same time on an Active Data Guard standby database. By default, ENABLE_IMC_WITH_MIRA is FALSE.
 

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