Re: By default, LOB store in line or out of line?

  • From: Tanel Poder <tanel@xxxxxxxxxxxxxx>
  • To: Leyi Kamus Zhang <kamusis@xxxxxxxxx>
  • Date: Sun, 22 Apr 2012 19:17:54 +0300

(reposting due to overquoting)
Yeah, LOBs over DBlinks are a problem. As every LOB item will require a
SQL*Net roundtrip ... thus there's a lot of idle time on both ends of the
dblink due to network latency. I don't think that even doing datapump *over
dblinks* changes this as it's how LOB access over OPI works (their data has
to be retrieved with a separate OPI call - it isn't bundled in the regular
row stream).

So unless you want to go with other approaches (like datapump'ing to a NFS
share and mounting it on the target server too) then you'll just need to
start tens or hundreds of connections, each fetching their own subset of
data.

You might end up with various contention issues (on LOB segments example),
especially if you don't have partitioned tables in the target system, but
it's matter of testing & benchmarking as usual.

Tanel.

On Sun, Apr 22, 2012 at 7:05 PM, Leyi Kamus Zhang <kamusis@xxxxxxxxx> wrote:

> Hi Tanel
>
> Thanks for your reply, I'm reading your ppt on slideshare, perfect one.
>
> One more question for BLOB performance, I knew you and Randy write the
> "Expert Oracle Exadata" Chaper 13, it's for migration to Exadata. Now I'm
> doing a huge database migration, not to Exadata, just from an Oracle
> database to another, in my test, we can only achieve 10MB/s when CTAS a
> table with BLOB, and only 25MB/s when CTAS a normal table without LOB
> columns(database link in 1000Mbps NIC), I'm wonder how fast the speed you
> can achieve?
>
> --
> Kamus <kamusis@xxxxxxxxx>
>
> Visit my blog for more : http://www.dbform.com
> Join ACOUG: http://www.acoug.org
>
>
>


--
//www.freelists.org/webpage/oracle-l


Other related posts: