Dbms_redefinition works well for this type of migration.
Original white paper on the move
(http://www.oracle.com/technetwork/database/securefilesmigrationpaper-130440.pdf).
There are a lot more papers you can look at online.
I would also do a search on support.oracle.com to look at current bugs relative
to your exact database version.
For 300GB, yes it could take a day or two depending on the performance of your
storage subsystem and the activity on the system/table.
There is always a chance of something failing or hanging the longer it runs.
You have the ability to change the storage options in the move as underneath
the covers dbms_redefintion is using a new table to move into.
Matthew Parker
Chief Technologist
Dimensional DBA
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From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Chen Zhou
Sent: Tuesday, February 09, 2016 2:11 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Moving BLOBs from BASICFILES to SECUREFILES
Hi,
We have this table with BLOBs, which has high "enq:HW- contention" from time to
time.
We already have event "44951 TRACE NAME CONTEXT FOREVER, LEVEL 1024" set. The
only option I can think of is to move this BLOB from BASICFILE to SECUREFILE.
There has been discussion of doing this by using dbms_redefinition here, it
seems to be a great tool that allows changing BLOB online.
This is a very important production database, will there be significant
performance impact using this tool? If so, we may just schedule a maintenance
time.
How long should we expect to redefine 300GB BLOBs? A few hours or a few days?
Can it end up hanging?
Can I take the opportunity to move the BLOB to another tablespace during this
redefinition process?
Thank you for your information.
Chen
