RE: IPC versus TCP performance

I agree with the optimizer question. At least a few versions ago, joining tables across a database link had poor performance. Anybody know if still true. >>> "Mark W. Farnham" <mwf_at_rsiz.com> 10/31/18 12:54 PM >>> And, (not but), if you're using sqlplus for this this traffic please be sure you've set arraysize to something bigger than the default of 15.

Recommendations vary from 100ish to 1024ish. Last time I measured 1024 seemed to work about best for a variety of situations and your mileage will vary by too many infrastructure details for my measurements to be useful. I'm not aware of any noticeable resource consumption or extra overhead from 1024.

Then, to answer Stefan's question, consider a profiler to tell you where the problem lies.

mwf

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Stefan Koehler Sent: Tuesday, October 30, 2018 4:28 PM
To: Amir.Hameed_at_xerox.com; ORACLE-L
Subject: Re: IPC versus TCP performance

Hello Amir,
are you sure that this is a communication (latency) problem over the database link and not an optimizer problem (e.g. bad execution plans) due to the involved remote tables (distributed query)?

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website: http://www.soocs.de

Twitter: _at_OracleSK

> "Hameed, Amir" <Amir.Hameed_at_xerox.com> hat am 30. Oktober 2018 um 14:01 geschrieben:
>
> Hi,
>
> I have two databases running on the same physical server. The OS is RHEL7. Database A is 11.2.0.4 and is running as Active Data Guard. Database B is a reporting database and is version 12.1.0.2. In the past, database A was running on Solaris (four-node RAC) and we were using Oracle Streams to replicate over 400 tables from this particular database over to database B. We were also replicating tables from multiple other databases to database B but that is beside the point for this discussion. After we converted database A to LINUX, we decided to keep database B as the front-end and created synonyms to access tables from database A (ADG) using DB links. We have also setup IPC communication between A and B assuming that IPC would be faster than TCP. Unless I have misconfigured IPC, so far the performance of accessing database from B-to-A over a DB link is abysmal. Before I ask users to start accessing A directly instead of going through B, I wanted to understand the IPC communication a
  bit better.
>
> In my scenario where both databases reside on the same physical server, is there a way to optimize access from B-to-A over a DB link?
>
> Thank you,
>
> Amir

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