菜鳥_Oracle space reclaim

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Oracle space reclaim.

Good acticles are it:
http://www.dba-oracle.com/t_reclaiming_disk_space.htm

Several techniques to reclaim space:
\1. Parameter
1.1 Alter database datafile xx dbf resize xxxm;
1.2 Alter tablespace xxx coalesce: reclaim space from honeycomb

Table level:
1. Export the table, drop and import the table, this is kind of re-organization
2. dbms_redefinition: also reorganize a table  but the table can remain online
3. alter table xxx shrink: shrink is to reclaim space fargmentation below the HWM and move it to above HWM, which result in a lower HWM.
4. alter tablexxx deallocate unused space: move the unused space toward the HWM and make available for use by other object. (Does it mean space are allocate above the HWM?)

More information about Space/Compression from Burleson Consulting:
http://www.dba-oracle.com/oracle11g/sf_Oracle_11g_Data_Compression_Tips_for_the_DBA.html