From: Dimensional DBA <>
Date: Tue, 9 Feb 2016 14:32:03 -0800
Message-ID: <002a01d16389$b3c979d0$1b5c6d70$>

Dbms_redefinition works well for this type of migration.

Original white paper on the move ( There are a lot more papers you can look at online.

I would also do a search on 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

425-891-7934 (cell)

D&B 047931344


<> View Matthew Parker's profile on LinkedIn

From: [] On Behalf Of Chen Zhou Sent: Tuesday, February 09, 2016 2:11 PM To:
Subject: Moving BLOBs from BASICFILES to SECUREFILES  


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.


Received on Tue Feb 09 2016 - 23:32:03 CET

Original text of this message