1.154 INMEMORY_VIRTUAL_COLUMNS
INMEMORY_VIRTUAL_COLUMNS
controls which user-defined virtual columns are stored as In-Memory virtual columns (IM columns).
Property | Description |
---|---|
Parameter type |
String |
Syntax |
|
Default value |
|
Modifiable |
|
Modifiable in a PDB |
Yes |
Basic |
No |
Oracle RAC |
The same value must be used on all instances. |
IM virtual columns improve query performance by avoiding the necessity of repeated calculations. Also, the database can scan and filter IM virtual columns using techniques such as SIMD vector processing.
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ENABLE
: For a table or partition that has been enabled for in-memory storage, all virtual columns will be stored in-memory at the default table or partition memcompress level unless:-
They have been explicitly excluded using the no inmemory syntax.
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They have been altered to have a different memcompress level than the base table or partition, in which case they will be stored at the specified memcompress level.
-
-
MANUAL
: This is the default value for the parameter. For a table or partition that has been enabled for in-memory storage, no virtual columns will be stored in-memory unless:-
They have been explicitly marked for inmemory, in which case they will be stored in-memory at the table or partition memcompress level.
-
They have been marked for inmemory with a different memcompress level than the base table or partition, in which case they will be stored at the specified memcompress level.
-
-
DISABLE
: For a table or partition that has been enabled for in-memory storage, no virtual columns will ever be stored in-memory. Any changes to the inmemory_column_clause for a virtual column including changes in memcompress level will be recorded, but not acted upon with regards to population of virtual columns.
See Also:
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Oracle Database In-Memory Guide for more information about IM virtual columns