You want to reclaim some valuable Oracle estate – disk space, from your datafile(s).
ALTER DATABASE DATAFILE … RESIZE can reclaim the space at the end of the datafile,
But if you tried it and got the error below, then you must have chosen some arbitrary values which tried to reclaim beyond that is possible.
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ORA-03297: file contains used data beyond requested RESIZE value |
There is a minimum value that you can’t go beyond called the ‘datafile high water mark’.
So, how do you find this minimum value – the datafile’s high water mark? Query the view dba_extents
WARNING!!
On a large database system, do not query the dba_extents view/table.You can query DBA_EXTENTS to know that. But It runs forever and is resource-intensive.
SO WHAT DO WE DO
We query SYS.X$KTFBUE instead, which is the underlying fixed table that gives extent allocation in Locally Managed Tablespaces.
Here is the query:
set linesize 1000 pagesize 0 feedback off trimspool onwith hwm as ( -- get highest block id from each datafiles ( from x$ktfbue as we don't need all joins from dba_extents ) select /*+ materialize */ ktfbuesegtsn ts#,ktfbuefno relative_fno,max(ktfbuebno+ktfbueblks-1) hwm_blocks from sys.x$ktfbue group by ktfbuefno,ktfbuesegtsn ), hwmts as ( -- join ts# with tablespace_name select name tablespace_name,relative_fno,hwm_blocks from hwm join v$tablespace using(ts#) ), hwmdf as ( -- join with datafiles, put 5M minimum for datafiles with no extents select file_name,nvl(hwm_blocks*(bytes/blocks),5*1024*1024) hwm_bytes,bytes,autoextensible,maxbytes from hwmts right join dba_data_files using(tablespace_name,relative_fno) )select case when autoextensible='YES' and maxbytes>=bytes then -- we generate resize statements only if autoextensible can grow back to current size '/* reclaim '||to_char(ceil((bytes-hwm_bytes)/1024/1024),999999) ||'M from '||to_char(ceil(bytes/1024/1024),999999)||'M */ ' ||'alter database datafile '''||file_name||''' resize '||ceil(hwm_bytes/1024/1024)||'M;' else -- generate only a comment when autoextensible is off '/* reclaim '||to_char(ceil((bytes-hwm_bytes)/1024/1024),999999) ||'M from '||to_char(ceil(bytes/1024/1024),999999) ||'M after setting autoextensible maxsize higher than current size for file ' || file_name||' */' end SQLfrom hwmdfwhere bytes-hwm_bytes>1024*1024 -- resize only if at least 1MB can be reclaimedorder by bytes-hwm_bytes desc//* reclaim 593M from 3072M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/euna_data_02.dbf’ resize 2480M;
/* reclaim 248M from 256M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/euna_rsa_data_01.dbf’ resize 9M;
/* reclaim 243M from 256M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/euna_rsa_idx_01.dbf’ resize 14M;
/* reclaim 141M from 142M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/users01.dbf’ resize 2M;
/* reclaim 41M from 710M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/sysaux01.dbf’ resize 670M;
/* reclaim 3M from 1390M */ alter database datafile ‘/u02/app/oracle/oradata/CHARLES/system01.dbf’ resize 1388M;
charlesajah 