Oracle | DBMS_INMEMORY

Oracle DBMS_INMEMORY_ADMIN Version 26ai

General Information

Library Note

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Oracle Database 26ai will be available on generic Linux platforms in January and soon on AIX and Windows

Purpose Provides interfaces for managing In-Memory Expressions (IM expressions) and the In-Memory FastStart (IM FastStart) area.

Analytic queries often contain complex expressions or calculations that can consume significant CPU and memory during execution. Use DBMS_INMEMORY_ADMIN procedure to identify these frequently used (�hot�) expressions and populate them in the IM column store. In this way, the database avoids repeated computations and improves performance.

AUTHID CURRENT_USER

Constants

Name	Data Type	Value
AIM Constants
AIM_SERIALIZATION	NUMBER	0
AIM_STATWINDOW_DAYS	NUMBER	1
AIM_STATWINDOW_DAYS_DEFAULT	NUMBER	2
Populate Wait Return Codes
POPULATE_TIMEOUT	NUMBER	-1
POPULATE_SUCCESS	NUMBER	0
POPULATE_OUT_OF_MEMORY	NUMBER	1
POPULATE_NO_INMEMORY_OBJECTS	NUMBER	2
POPULATE_INMEMORY_SIZE_ZERO	NUMBER	3

Dependencies

ADO_IMPARAM$	DBMS_INMEMORY_LIB	IM_IME$
DBA_IM_EXPRESSIONS	DBMS_STANDARD	PRVT_DBMS_INMEMORY_ADMIN
DBMS_INMEMORY

Documented Yes: Packages and Types Reference

First Available 12.2

Security Model Owned by SYS with EXECUTE granted to the DBA role

Source {ORACLE_HOME}/rdbms/admin/dbmsinmemadmin.sql

Subprograms

AIM_GET_PARAMETER	FASTSTART_MIGRATE_STORAGE	IME_GET_CAPTURE_STATE
AIM_SET_PARAMETER	GET_FASTSTART_TABLESPACE	IME_OPEN_CAPTURE_WINDOW
DEALLOCATE_VERSIONS	IME_CAPTURE_EXPRESSIONS	IME_POPULATE_EXPRESSIONS
FASTSTART_CHECKPOINT	IME_CLOSE_CAPTURE_WINDOW	POPULATE_WAIT
FASTSTART_DISABLE	IME_DROP_ALL_EXPRESSIONS	SET_SGA_PERCENTAGE
FASTSTART_ENABLE

AIM_GET_PARAMETER

Returns the current value of an AIM parameter dbms_inmemory_admin.aim_get_parameter( parameter IN NUMBER, value OUT NUMBER);

DECLARE

       outVal NUMBER;

      BEGIN

        dbms_inmemory_admin.aim_get_parameter(dbms_inmemory_admin.aim_statwindow_days, outVal);

        dbms_output.put_line(TO_CHAR(outVal));

      END;

      /

AIM_SET_PARAMETER

Customizes the AIM execution environment dbms_inmemory_admin.aim_set_parameter( parameter IN NUMBER, value IN NUMBER);

exec dbms_inmemory_admin.aim_set_parameter(dbms_inmemory_admin.aim_statwindow_days, 30);

DEALLOCATE_VERSIONS

Disables the In-Memory FastStart (IM FastStart) feature dbms_inmemory_admin.deallocate_version(spcpressure IN BOOLEAN DEFAULT FALSE);

exec dbms_inmemory_admin.deallocate_version(TRUE);

FASTSTART_CHECKPOINT

Checkpoint all deferred write pending tasks immediately dbms_inmemory_admin.faststart_checkpoint(global IN BOOLEAN DEFAULT TRUE);

exec dbms_inmemory_admin.faststart_checkpoint(TRUE);

FASTSTART_DISABLE

Disables the faststart mechanism dbms_inmemory_admin.fasttart_disable;

See FASTSTART_ENABLE demo below

FASTSTART_ENABLE

Enables IM FastStart and assigns a tablespace dbms_inmemory_admin.faststart_enable( tbs_name IN VARCHAR2, nologging IN BOOLEAN DEFAULT TRUE);

CREATE TABLESPACE fs_tbs DATAFILE 'fs_tbs.dbf' SIZE 500M EXTENT MANAGEMENT LOCAL SEGMENT SPACE MANAGEMENT AUTO;

      

      exec dbms_inmemory_admin.faststart_enable('fs_tbs');

      

      The following query shows that the IM FastStart LOB was created (sample output included):

      col owner format a5

      col segment_name format a20

      

      SELECT l.owner, l.segment_name, SUM(s.bytes)/1024/1024 MB

      FROM dbs_lobs l, dba_segments s

      WHERE l.segment_name = s.segment_name

      AND l.tablespace_name = 'FS_TBS'

      GROUP BY l.owner, l.segment_name;

      

      OWNER  SEGMENT_NAME                 MB

      ------ -------------------- ----------

      SYS    SYSDBIMFS_LOBSEG$          .125

      

      drop tablespace fs_tbs including contents and datafiles;

      *

      ORA-64379: Action cannot be performed on the tablespace assigned to FastStart while the feature is enabled

      

      exec dbms_inmemory_admin.faststart_disable;

      

      DROP TABLESPACE fs_tbs INCLUDING CONTENTS AND DATAFILES;

FASTSTART_MIGRATE_STORAGE

Moves all IM FastStart data and metadata from the existing tablespace to the specified new tablespace dbms_inmemory_admin.faststart_migrate_storage(tbs_name IN VARCHAR2);

exec dbms_inmemory_admin.faststart_migrate_storage('UWFS');

GET_FASTSTART_TABLESPACE

Returns the name of the tablespace that is currently designated for IM FastStart dbms_inmemory_admin.get_faststart_tablespace RETURN VARCHAR2;

-- seriously ... this is not an error ... Oracle actually used VARCHAR rather than VARCHAR2 ... we are not impressed.

SELECT dbms_inmemory_admin.get_faststart_tablespace;

      

      GET_FASTSTART_TABLESPACE

      -------------------------

      NOT ENABLED

IME_CAPTURE_EXPRESSIONS

Captures and populates the 20 most frequently accessed (�hottest�) expressions in the database in the specified time range. dbms_inmemory_admin.ime_capture_expressions(snapshot IN VARCHAR2); Valid values are CUMULATIVE and CURRENT (most recent 24 hours)

exec dbms_inmemory_admin.ime_capture_expressions('CURRENT');

      

      PL/SQL procedure successfully completed.

IME_CLOSE_CAPTURE_WINDOW

Closes an expression monitoring window dbms_inmemory_admin.ime_close_capture_window;

exec dbms_inmemory_admin.ime_close_capture_window;

      

      PL/SQL procedure successfully completed.

IME_DROP_ALL_EXPRESSIONS

Drops all SYS_IME hidden VCs across all tables in the database whether they are marked for in-memory or not dbms_inmemory_admin.ime_drop_all_expressions;

exec dbms_inmemory_admin.ime_drop_all_expressions;

      

      PL/SQL procedure successfully completed.

IME_GET_CAPTURE_STATE

Returns the current state of the expression monitoring window dbms_inmemory_admin.ime_get_capture_state( p_capture_state OUT VARCHAR2, p_last_modified OUT TIMESTAMP);

DECLARE

       stateVal VARCHAR2(60);

       lastMod  TIMESTAMP;

      BEGIN

        dbms_inmemory_admin.ime_get_capture_state(stateVal, lastMod);

        dbms_output.put_line(stateVal);

        dbms_output.put_line(lastMod);

      END;

      /

IME_OPEN_CAPTURE_WINDOW

Opens an expression monitoring window dbms_inmemory_admin.ime_open_capture_window;

exec dbms_inmemory_admin.ime_open_capture_window;

      

      PL/SQL procedure successfully completed.

IME_POPULATE_EXPRESSIONS

Populates all hot expressions that were captured in the latest iteration, into the IM column store dbms_inmemory_admin.ime_populate_expressions;

exec dbms_inmemory_admin.ime_populate_expressions;

      

      PL/SQL procedure successfully completed.

POPULATE_WAIT

Wrapper around populate() that waits for population to finish for all inmemory objects with priority greater than or equal to the priority specified (default LOW) dbms_inmemory_admin.populate_wait( priority IN VARCHAR2 DEFAULT 'LOW', percentage IN NUMBER DEFAULT 100, timeout IN NUMBER DEFAULT 9999999, force IN BOOLEAN DEFAULT FALSE) RETURN NUMBER;

DECLARE

       retVal NUMBER;

      BEGIN

        retVal := dbms_inmemory_admin.populate_wait(force=>TRUE);

        dbms_output.put_line(TO_CHAR(retVal));

      END;

      /

      POPULATE ERROR, INMEMORY_SIZE=0

      3

SET_SGA_PERCENTAGE (new 23ai)

sets an underscore parameter setting the background resize SGA targer dbms_inmemory_admin.aim_set_sga_percentage(sga_percent IN NUMBER);

exec dbms_inmemory_admin.set_sga_percentage(6);

      

      PL/SQL procedure successfully completed.

      

      SQL> sho parameter _inmem

      

      NAME                                   TYPE    VALUE

      -------------------------------------- ------- -----

      _inmemory_bg_resize_target_sga_percent integer     6