Re: Moving BLOBs from BASICFILES to SECUREFILES

From: Chen Zhou <oracle.unknowns_at_gmail.com>
Date: Tue, 9 Feb 2016 16:30:09 -0800
Message-ID: <CAJUY3dQh0PWbmG+OH7+izY33WGbb-sAaZxP1hDEH50-fA0ZjeQ_at_mail.gmail.com>

Matthew and Andrew,
Thank you very much for the information. It sounds like a safe option. I will test it first, then run it in production.
Regards,
Chen

On Tue, Feb 9, 2016 at 2:42 PM, Dimensional DBA <dimensional.dba_at_comcast.net
> wrote:

> …and you shouldn’t worry about it hanging if you really decide to do it
> online, as all the operations of writes happen to the alternate table(
> materialized view). If it hangs then kill the session and start over if you
> have to.
>
>
>
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>
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> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *Andrew Kerber
> *Sent:* Tuesday, February 09, 2016 2:36 PM
> *To:* Chen Zhou
> *Cc:* oracle-l_at_freelists.org
> *Subject:* Re: Moving BLOBs from BASICFILES to SECUREFILES
>
>
>
> DBMS redefinition is the way to go. This is an online operation using
> dbms_redefinition, so down time is not required. Just do a periodic
> 'sync_interim_table' so the final switch doesnt take too long.
>
> However, there is no way anyone here knows the characteristics of your
> system, or how long it will take to move 300G of blobs. Any estimates we
> give would be purely guesswork.
>
> I did a blog on the use of dbms_redefinition some time ago, linked here:
>
> https://dbakerber.wordpress.com/2015/03/03/dbms_redefinition-revisited/
>
> I think it provides a pretty good example.
>
>
>
>
>
> On Tue, Feb 9, 2016 at 4:10 PM, Chen Zhou <oracle.unknowns_at_gmail.com>
> wrote:
>
> 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
>
>
>
>
> --
>
> Andrew W. Kerber
>
> 'If at first you dont succeed, dont take up skydiving.'
>

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Received on Wed Feb 10 2016 - 01:30:09 CET