Thinking Out Loud

April 16, 2017

Be Prepared When Using DBFS

Filed under: 12c,GoldenGate,oracle — mdinh @ 9:18 pm

Goldegate 12c implementation for 2-node RAC with XAG from Grid Home using DBFS.

We are facing situation where DBFS has 41G free while DBFS_TS has 1.5G free and having to resize BIGFILE tablespace.

Tablespace and DBFS size is 45G.

Basically, 45G tablespace is used to maintain 4G Goldengate files.

Based on steps followed from NOTE:1453350.1 – How to Determine what storage is used in a LOBSEGMENT and should it be shrunk / reorganized?

Next step is to Shrink a SECUREFILE LOB using Online Redefinition (DBMS_REDEFINITION)? (Document  1394613.1)

At this point, does not look pretty.

Here are all the research I have gone through.

NOTE:1150157.1 - List of Critical Patches Required For Oracle 11.2 DBFS and DBFS Client
BUG:13824914 - DBFS FREE SPACE IS NOT RECLAIMED AFTER DELETIONS.
BUG:12662040 - SECUREFILE LOB SEGMENT KEEPS GROWING IN CASE OF PLENTY OF FREE SPACE

How DBFS Reclaims Free Space After Files Are Deleted (Doc ID 1438356.1) 
NOTE:162345.1 - LOBS - Storage, Read-consistency and Rollback
NOTE:386341.1 - How to determine the actual size of the LOB segments and how to free the deleted/unused space above/below the HWM
--------------------------------------------------------------------------------
NOTE:1453350.1 - How to Determine what storage is used in a LOBSEGMENT and should it be shrunk / reorganized?
3) Determine if the LOBSEGMENT is a candidate for shrink / reorganization

The following query will show the extents allocated for the LOBSEGMENT

SELECT BYTES, COUNT(*) FROM DBA_EXTENTS WHERE SEGMENT_NAME = ''  GROUP BY BYTES ORDER BY 2;

If NON Data Bytes is  one or more of the extent sizes from this query ...
     then this segment is a candiate for a shrink / reorganization as this process will likely be able to reduce the size of the LOBSEGMENT by at least one extent

4) If #3 is true ... then the method in the following note may be used to shrink / reorganize the lob segment

How to Shrink a SECUREFILE LOB using Online Redefinition (DBMS_REDEFINITION)? (Document  1394613.1)
--------------------------------------------------------------------------------
NOTE:66431.1 - LOBS - Storage, Redo and Performance Issues
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