oracle filev$transaction oracle 12c database. oracle –12c database a temporary tablespace is used...
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Oracle – 12c Undo
The Undo Tablespace is used for Automatic Undo Management.
Used to Store Undo Segments
Cannot contain any other Objects
Extents are locally managed
Can only use the DATAFILE and EXTENT MANAGEMENT Clauses.
Undo tablespaces are used to store original data after it has been changed.
If user rollback the transaction the undo tablespace is used to back the data.
More than One Undo tablesapce available in Single database.
if we didn’t create any undo tablespace, then system undo used default.
Undo Tablespace
Oracle – 12c Database
Undo Purpose
Rolling back transactions explicitly with a ROLLBACK command
Rolling back transactions implicitly (automatic instance recovery)
Reconstructing readconsistent image of data
Recovering from logical corruptions
Oracle – 12c Undo
SQL> create undo tablespace undotbs
2 '/u01/app/oracle/oradata/SDBTDB/datafile/undo.dbf‘ size 100m;
Tablespace created.
Create Undo Tablespace
Oracle – 12c Undo
Undo Manage
SQL> alter system set undo_management=auto scope=spfile;
System altered.
SQL> show parameter undo_management
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_management string AUTO
Oracle – 12c Undo
Undo tablespace Switch
SQL> show parameter undo_tablespace;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_tablespace string UNDOTBS1
SQL> alter system set undo_tablespace=undotbs;
System altered.
SQL> show parameter undo_tablespace;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_tablespace string UNDOTBS
Oracle – 12c Undo
Drop a Undo Tablespace
SQL> drop tablespace undo1;
Tablespace dropped.
Oracle – 12c Undo
Undo tablespace guarantee
SQL> alter tablespace undotbs retention guarantee;
Tablespace altered.
SQL> alter tablespace undotbs retention noguarantee;
Tablespace altered.
Oracle – 12c Undo
Oracle 12c Undo Management
See current undo blocks
select begin_time, undotsn, undoblks,
activeblks, unexpiredblks, expiredblks
from v$undostat;
Contains snapshots of v$undostat (use obtain the oldest undo available)
select begin_time, undotsn, undoblks,
activeblks, unexpiredblks, expiredblks
From dba_hist_undostat;
Oracle – 12c Database
Oracle 12c Database
SQL> show parameter undo
NAME TYPE VALUE
------------------------------- ----------- -----------------
undo_management string AUTO
undo_retention integer 900
undo_tablespace string UNDOTBS1
Oracle – 12c Database
v$undostat
v$tempundostat
dba_hist_undostat
dba_undo_extents
dba_rollback_segs
v$rollname
v$rollstat
v$transaction
Oracle 12c Database
Oracle – 12c Database
A Temporary Tablespace is used to manage space for sort operations.
SQL queries are less likely to run out of space.
Database specify multiple default temporary tablespaces at the db level
Parallel execution can utilize multiple temporary tablespaces
single user can simultaneously use multiple temp tablespaces in different sessions.
Temporary Tablesapce
Oracle – 12c Database
Used for Sort Operations
Cannot contain any Permanent Objects.
Locally Managed Extents recommeded.
Tempfiles are also in a NOLOGGING Mode.
Tempfiles cannot be made read only or be renamed.
Tempifiles are required for read-only databases.
Temporary Tablesapce
Oracle – 12c Temporary
Temporary Tablesapce
SQL> select file_id,tablespace_name,bytes/1024/1024 "Size“
2 from dba_temp_files;
FILE_ID TABLESPACE_NAME Size
---------- ------------------------------ ----------
1 TEMP 131
2 TEMPTBS 50
SQL> create temporary tablespace temptbs
2 tempfile '/u01/app/oracle/oradata/SDBTDB/datafile/temp02.dbf'
3 size 50m;
Tablespace created.
Oracle – 12c Temporary
Database Temporary Tablesapce
SQL> alter database default temporary tablespace temptbs;
Database altered.
SQL> select * from database_properties
2 where property_name='DEFAULT_TEMP_TABLESPACE';
PROPERTY_NAME PROPERTY_VALUE
------------------------------ ------------------------------
DESCRIPTION
------------------------------------
DEFAULT_TEMP_TABLESPACE TEMPTBS
Name of default temporary tablespace
Oracle – 12c Temporary
Temporary Tablesapce Autoextend
SQL> alter database tempfile
2 '/u01/app/oracle/oradata/SDBTDB/datafile/temp02.dbf'
3 autoextend on;
Database altered.
Oracle – 12c Temporary
Temporary Tablesapce Autoextend
SQL> select file_name, autoextensible
2 from dba_temp_files;
FILE_NAME
--------------------------------------------------------------------------------
AUT
---
/u01/app/oracle/oradata/SDBTDB/datafile/o1_mf_temp_fsgmx5y2_.tmp
YES
/u01/app/oracle/oradata/SDBTDB/datafile/temp02.dbf
YES
Oracle – 12c Temporary
Temporary Tablesapce Resize
SQL> alter database tempfile 2 resize 80m;
Database altered.
SQL> select file_id,tablespace_name,bytes/1024/1024 "Size"
2 from dba_temp_files ;
FILE_ID TABLESPACE_NAME Size
---------- ------------------------------ ----------
1 TEMP 131
2 TEMPTBS 80
Oracle – 12c Temporary
Temporary Tablesapce Rename
SQL> alter database rename
2 file '/u01/app/oracle/oradata/SDBT/datafile/o1_mf_temp_fsfhy86q_.tmp'
3 to '/u01/app/oracle/oradata/SDBT/datafile/temp01.dbf‘;
Database altered.
Oracle – 12c Database
SQL> alter database tempfile 1 offline;
Database altered.
SQL> select file_id, tablespace_name, status
2 from dba_temp_files;
FILE_ID TABLESPACE_NAME STATUS
---------- -------------------------- -----------
2 TEMPTBS ONLINE
1 TEMP OFFLINE
Tempfile Status
Oracle – 12c Database
SQL> alter database tempfile 1 drop;
Database altered.
SQL> select file_id, tablespace_name, status
2 from dba_temp_files;
FILE_ID TABLESPACE_NAME STATUS
---------- -------------------------- -----------
2 TEMPTBS ONLINE
Drop a Tempfile
Oracle – 12c Database
V$tempfile
dba_temp_files
Dba_tablespace_groups
V$sort_segment
V$tempseg_usage
Temporary Tablesapce
