Guenadi N Jilevski's Oracle BLOG

CleanUp Temporary Segments Occupying Permanent Tablespace

CleanUp Temporary Segments Occupying Permanent Tablespace

There are situations when we see “temporary segments” in permanent tablespaces hanging around and not getting cleaned up.
These temporary segments in permanent tablespace can be created by DDL operations like CTAS and “alter index..rebuild” because the new object is created as a temporary segment in the target tablespace.
These temporary segments take actual disk space when SMON fails to perform its assigned job to cleanup stray temporary segments.
Following query finds out these segments:

SQL > select tablespace_name, owner, sum(bytes/1024/1024) from dba_segments
where segment_type = ‘TEMPORARY’ group by tablespace_name, owner;

TABLESPACE_NAME          OWNER              SUM(BYTES/1024/1024)
——————-                    ————        ——————–
xxxx_DATA                             BLD                     137706
KPMGRT_INDEX                    BLD                       8910
KPMGRT_DATA                      BLD                  25284.875
BILL_INDEX                             BLD                        .25
CELL_DATA                              BLD                        798
CELL_INDEX                            BLD                        208
CSC_DATA                                BLD                   69642.25
CSC_INDEX                              BLD                   956.4375

Here we can see that tablespace KPMGRT_DATA, CSC_INDEX and CSC_DATA have large temporary segments.
To find out if any DDL is active which can create temporary segments we can use the following:

SQL> conn / as sysdba
SQL> select owner FROM dba_segments WHERE segment_name='<name>’;
SQL> select pid from v$process where username=’owner from above query’;
SQL> alter session set tracefile_identifier=’TEMPORARY_SEGMENTS’;
SQL> oradebug setorapid
SQL> oradebug dump errorstack 3
SQL > oradebug tracefile_name

Above  will produce the tracefile name, open that file and check for the “current sql”
If it is a DDL like CTAS or index rebuild, then wait for the operation to complete. If there is no pid
returned then these segments are “stray segements” and needs to cleaned up manually.
There are two ways to force the drop of temporary segments:

1. Using event DROP_SEGMENTS

2. Corrupting the segments and dropping these corrupted segments.

A. Using DROP_segments:

Find out the tablespace number (ts#) which contains temporary segments:

SQL> select ts# from sys.ts$ where name = ‘tablespace name’;

Suppose it comes out to be 10, use the following command to cleanup temporary segments:

SQL> alter session set events ‘immediate trace name DROP_SEGMENTS level 11’;

level is ts#+1 i.e 10+1=11 in this case.

B. Corrupting temporary segments for drop:

For this following procedures are used:

– DBMS_SPACE_ADMIN.TABLESPACE_VERIFY
– DBMS_SPACE_ADMIN.SEGMENT_CORRUPT
– DBMS_SPACE_ADMIN.SEGMENT_DROP_CORRUPT
– Verify the tablespace that contains temporary segments (In this case it is KPMGRT_DATA)

SQL> exec DBMS_SPACE_ADMIN.TABLESPACE_VERIFY(‘KPMGRT_DATA’);– Corrupt the temporary segments in tablespace KPMGRT_DATA
SQL> select ‘exec DBMS_SPACE_ADMIN.SEGMENT_CORRUPT(‘ || chr(39) || tablespace_name || chr(39) || ‘,’ || HEADER_FILE || ‘,’ || HEADER_BLOCK || ‘);’  from dba_segments where SEGMENT_TYPE like ‘TEMP%’ and tablespace_name = ‘KPMGRT_DATA’;– Drop the corrupted temporary segments
SQL> select ‘exec DBMS_SPACE_ADMIN.SEGMENT_DROP_CORRUPT (‘ || chr(39) || tablespace_name || chr(39) || ‘,’ || HEADER_FILE || ‘,’ || HEADER_BLOCK || ‘);’ from dba_segments where SEGMENT_TYPE like ‘TEMP%’ and tablespace_name = ‘KPMGRT_DATA’;– Verify the tablespace again to update the new dictionary information:
SQL> EXECUTE DBMS_SPACE_ADMIN.TABLESPACE_VERIFY(‘KPMGRT_DATA’);This will remove temporary segments from permanent tablespace.

March 5, 2009 - Posted by gjilevski | oracle