Oracle | System and ALTER SYSTEM

Oracle Alter System Version 21c

General Information

Library Note

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Purpose Quote from the online docs at http://docs.oracle.com:
"Use the ALTER SYSTEM statement to dynamically alter your Oracle Database instance. The settings stay in effect as long as the database is mounted. When you use the ALTER SYSTEM statement in a multitenant container database (CDB), you can specify some clauses to alter the CDB as a whole and other clauses to alter a specific pluggable database (PDB)"

Data Dictionary conn / as sysdba desc v$parameter SELECT issys_modifiable, COUNT(*) FROM v$parameter GROUP BY issys_modifiable; SELECT ispdb_modifiable, COUNT(*) FROM v$parameter GROUP BY ispdb_modifiable; SELECT isinstance_modifiable, COUNT(*) FROM v$parameter GROUP BY isinstance_modifiable; -- parameters changed during installation SELECT ismodified, COUNT(*) FROM v$parameter GROUP BY ismodified; SELECT name, value FROM v$parameter WHERE ismodified = 'MODIFIED'; -- parameters changed following installation SELECT isadjusted, COUNT(*) FROM v$parameter GROUP BY isadjusted; SELECT name, value FROM v$parameter WHERE isadjusted = 'TRUE'; -- deprecated parameters: make sure you are not setting any col name format a32 col value format a49 SELECT name, value FROM v$parameter WHERE isdeprecated = 'TRUE';

System Privileges

ALTER SYSTEM

Affinity ALTER SYSTEM <DISABLE | ENABLE> AFFINITY [schema_name.]<table_name> [SERVICE <service_name>];

ALTER SYSTEM ENABLE AFFINITY uwclass.servers SERVICE pdbdev;

      

      ALTER SYSTEM DISABLE AFFINITY uwclass.servers;

Archive Log ALTER SYSTEM <archivelog clause>

Follow the "ARCHIVELOG" Link in the Related Topics Section at Page Bottom

Cancel SQL ALTER SYSTEM CANCEL SQL '<session_id,serial_number>[,@instance_id][SQL_ID]';

ALTER SYSTEM CANCEL SQL '6,51659,@1';

Checkpoint ALTER SYSTEM CHECKPOINT [GLOBAL];

ALTER SYSTEM CHECKPOINT;

Check Datafiles -- only valid with a RAC configuration: Global indicates all instances ALTER SYSTEM CHECK DATAFILE <GLOBAL | LOCAL>;

ALTER SYSTEM CHECK DATAFILES LOCAL;

Commit ALTER SYSTEM <commit clause>

Follow the "TRANSACTIONS" Link in the Related Topics Section at Page Bottom

Distributed Recovery ALTER SYSTEM <ENABLE | DISABLE> DISTRIBUTED RECOVERY;

ALTER SYSTEM enable DISTRIBUTED RECOVERY;

      

      ALTER SYSTEM disable DISTRIBUTED RECOVERY;

Disconnect Session ALTER SYSTEM DISCONNECT SESSION '<SID>,<SERIAL#>' [POST_TRANSACTION] [< IMMEDIATE | NOREPLAY>];

set linesize 121

      

      SELECT sid, serial#, osuser, username, schemaname

      FROM v$session

      WHERE sid = (SELECT sid FROM v_$mystat WHERE rownum = 1);

      

      ALTER SYSTEM DISCONNECT SESSION '8,694' POST_TRANSACTION;

Flush Buffer Cache ALTER SYSTEM FLUSH BUFFER_CACHE;

ALTER SYSTEM FLUSH BUFFER_CACHE;

ALTER SYSTEM FLUSH BUFFER_POOL DEFAULT;

Flush Flash Cache ALTER SYSTEM FLUSH FLASH_CACHE;

ALTER SYSTEM FLUSH FLASH_CACHE;

Flush Flash Global Context ALTER SYSTEM FLUSH GLOBAL CONTEXT;

ALTER SYSTEM FLUSH GLOBAL CONTEXT;

Flush Global Context ALTER SYSTEM FLUSH GLOBAL CONTEXT;

ALTER SYSTEM FLUSH GLOBAL CONTEXT;

Flush Password File Metadata Cache ALTER SYSTEM FLUSH PASSWORDFILE_METADATA_CACHE;

ALTER SYSTEM FLUSH PASSWORDFILE_METADATA_CACHE;

Flush Redo ALTER SYSTEM FLUSH REDO TO <target_db_name> [[NO] [CONFIRM] [APPLY]]

SELECT name

      FROM v$database;

      

      ALTER DATABASE CLOSE;

      

      ALTER SYSTEM FLUSH REDO TO orabase CONFIRM APPLY;

Flush Shared Pool ALTER SYSTEM FLUSH SHARED_POOL;

ALTER SYSTEM FLUSH SHARED_POOL;

Kill Session ALTER SYSTEM KILL SESSION '<SID>,<SERIAL#>[, @INSTANCE_NUMBER]' [< IMMEDIATE | NOREPLAY>];

set linesize 121

      

      SELECT sid, serial#, osuser, username, schemaname

      FROM v_$session

      WHERE sid = (SELECT sid FROM v$mystat WHERE rownum = 1);

      

      ALTER SYSTEM  KILL SESSION '8,694';

      

      ALTER SYSTEM  KILL SESSION '8,694,@2';

      

      ALTER SYSTEM  KILL SESSION '8,694,@2' IMMEDIATE;

Determine if a killed session is rolling back a transactions This shows the user who's transaction is being rolled back If this number, xidusn, is decreasing then the transaction is rolling back. If it is increasing then the transaction is moving forward.

SELECT a.sid, a.username, b.xidusn rollback_seg_no,

      b.used_urec undo_records, b.used_ublk undo_blocks

      FROM gv$session a, gv$transaction b

      WHERE a.saddr = b.ses_addr;

Listener Registration ALTER SYSTEM REGISTER;

ALTER SYSTEM REGISTER;

Local Listener Registration ALTER SYSTEM SET LOCAL_LISTENER='<listener_name>';

ALTER SYSTEM SET LOCAL_LISTENER = 'CDB_LISTENER';

Quiesce ALTER SYSTEM <QUIESCE [RESTRCTED] | UNQUIESS>;

-- only valid in conjunction with DBMS_RESOURCE_MANAGER

      ALTER SYSTEM QUIESCE;

      ALTER SYSTEM UNQUIESCE;

Relocate Client ALTER SYSTEM <relocate client clause> is relevant only with Oracle Flex ASM and is not covered in the Library

TBD

Remote Listener Registration ALTER SYSTEM SET REMOTE_LISTENER='<listener_name>';

ALTER SYSTEM SET REMOTE_LISTENER = 'DG_LISTENER';

Reset ALTER SYSTEM SET <parameter_name> RESET;

See the "Reset Parameter Value" section of this page below

Restricted Session ALTER SYSTEM <ENABLE | DISABLE> RESTRICTED SESSION;

ALTER SYSTEM ENABLE RESTRICTED SESSION;

      ALTER SYSTEM DISABLE RESTRICTED SESSION;

Resume ALTER SYSTEM RESUME;

ALTER SYSTEM RESUME;

Rolling Migration (Start) ALTER SYSTEM START ROLLING MIGRATON TO '<asm_version>'

TBD

Rolling Migration (Stop) ALTER SYSTEM STOP ROLLING MIGRATION

ALTER SYSTEM STOP ROLLING PATCH;

Rolling Patch ALTER SYSTEM <START | STOP> ROLLING PATCH

ALTER SYSTEM START ROLLING PATCH;

Set ALTER SYSTEM SET <parameter_name> = <value> COMMENT, SID, CONTAINER, SCOPE

Follow the "STARTUP PARAMETERS" Link in the Related Topics Section at Page Bottom

Shutdown Dispatcher -- only valid with a shared server configuration something best avoided and thus this is not covered in the Library ALTER SYSTEM SHUTDOWN [IMMEDIATE] <dispatcher_name>;

Suspend ALTER SYSTEM SUSPEND;

ALTER SYSTEM SUSPEND;

Switch Logfile ALTER SYSTEM SWITCH LOGFILE;

ALTER SYSTEM SWITCH LOGFILE;

Wallet Close ALTER SYSTEM SET <encyption wallet> CLOSE IDENTIFIED BY "<wallet_password | hsm_aut_string>"

Follow the "STARTUP "WALLET" Link in the Related Topics Section at Page Bottom

Wallet Open ALTER SYSTEM SET <encyption wallet> OPEN IDENTIFIED BY "<wallet_password | hsm_aut_string>"

Follow the "STARTUP "WALLET" Link in the Related Topics Section at Page Bottom

Wallet Set Encryption Key ALTER SYSTEM SET ENCRYPTION KEY ...

Follow the "STARTUP "WALLET" Link in the Related Topics Section at Page Bottom

Set Parameter Value

Full Syntax ALTER SYSTEM SET <parameter_name> = <value> [COMMENT='<comment_string>'] [CONTAINER=<ALL | CURRENT>] [DEFERRED] [SID = '<sid_name>'] [SCOPE = <BOTH | MEMORY | SPFILE>];

Comment

Allow the association of a comment string with this change in the value of the parameter. If SPFILE is specified the comment will be written to the file. ALTER SYSTEM SET <parameter_name> = <value> [COMMENT '<comment_string>'];

ALTER SYSTEM SET audit_sys_operations=TRUE

      COMMENT='Begin auditing SYS'

      CONTAINER = ALL

      SCOPE=SPFILE;

Container

If the ALTER SYSTEM commands will affect a specific PDB rather than all PDBs specify this clause ALTER SYSTEM SET <parameter_name> = <value> [CONTAINER=<ALL | CURRENT>];

conn sys@pdbdev as sysdba

      

      ALTER SYSTEM SET plsql_code_type=NATIVE

      CONTAINER=CURRENT;

Deferred

Most ALTER SYSTEM commands can use the DEFERRED suffix to modify all future sessions but not affect the current session ALTER SYSTEM SET <parameter_name> = <value> [DEFERRED];

conn sys@pdbdev as sysdba

      

      ALTER SYSTEM SET plsql_code_type=NATIVE DEFERRED;

Reset

Return the value of a parameter to its original installation default ALTER SYSTEM RESET <parameter_name> SCOPE = SPFILE; ALTER SYSTEM RESET <parameter_name> [SID = '<sid_name | *>'];

ALTER SYSTEM RESET plsql_code_type SCOPE=SPFILE;

      

      ALTER SYSTEM RESET plsql_code_type SID='*';

Scope

Note MEMORY indicates that the change is made in memory, takes effect immediately, and persists until the database is shut down.

SPFILE indicates that the change is made in the server parameter file and will only take affect after the database is restarted.

BOTH indicates that the change is made in memory and in the server parameter file.

Specifies when the change takes effect. Scope only affects databases using an SPFILE. With databases started using a PFILE all ALTER SYSTEM commands affect only memory. ALTER SYSTEM SET <parameter_name> = <value> [SCOPE = <BOTH | MEMORY | SPFILE>];

ALTER SYSTEM SET  plsql_code_type = 'NATIVE'

      SCOPE=MEMORY;

      

      ALTER SYSTEM SET audit_sys_operations=TRUE

      SCOPE=SPFILE;

      

      ALTER SYSTEM SET plsql_code_type = 'NATIVE'

      SCOPE=BOTH;

SID

Use on a RAC cluster to identify a specific instance

* = all ALTER SYSTEM SET <parameter_name> = <value> [SID = '<sid_name | *>'];

conn / as sysdba

      

      SELECT instance_name

      FROM v$instance;

      

      ALTER SYSTEM SET plsql_code_type = 'NATIVE'

      SID = 'orabase';

Related Demos

Is the SGA performing sizing dynamic SQL> show parameter sga_max_size SQL> show sga Total System Global Area 2505338880 bytes Fixed Size 2405760 bytes Variable Size 637536896 bytes Database Buffers 1845493760 bytes Redo Buffers 19902464 bytes SQL> ALTER SYSTEM SET sga_max_size=2400M SCOPE=SPFILE; System altered. SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> startup; ORACLE instance started. Total System Global Area 2505338880 bytes Fixed Size 2405760 bytes Variable Size 671091328 bytes Database Buffers 1811939328 bytes Redo Buffers 19902464 bytes Database mounted. Database opened. SQL> ALTER SYSTEM SET sga_max_size=180M; * ERROR at line 1: ORA-02095: specified initialization parameter cannot be modified

Which proves two things. First, if you set SGA_MAX_SIZE to 2400M then the next time you start your instance, a full 2.5GB of RAM is used by the SGA (give or take a bit of rounding up to the next granule border). Yet I changed nothing to do with my shared pool, my buffer cache or my large pool ... so clearly, the *used* bit of my SGA can only be the same as it was before ... as is evidenced by the before and after values displayed for the "Database Buffers" and "Redo Buffers" components, for example.

Secondly, how "dynamic" is the SGA when the parameter which sizes it, SGA_MAX_SIZE, can't actually be dynamically altered, as I demonstrate at the end with an attempt to dynamically set it to 180M: It can only be modified with the 'scope=spfile' clause requiring an instance re-start before the new value is read.

SGA_MAX_SIZE is not actually dynamic, and, SGA_MAX_SIZE steals all of its memory from the operating system regardless of what your caches and pools are set to.

Different operating systems, for example Solaris, may behave differently.