Return-Path: Received: from newsfeed.cts.com (newsfeed.cts.com [209.68.248.164]) by naude.co.za (8.11.2/8.11.2) with SMTP id g5726d705480 for ; Thu, 6 Jun 2002 22:06:39 -0400 Received: from fatcity.UUCP (uucp@localhost) by newsfeed.cts.com (8.9.3/8.9.3) with UUCP id LAA57655; Thu, 6 Jun 2002 11:00:52 -0700 (PDT) Received: by fatcity.com (26-Feb-2001/v1.0g-b71/bab) via UUCP id 004766B1; Thu, 06 Jun 2002 09:58:28 -0800 Message-ID: Date: Thu, 06 Jun 2002 09:58:28 -0800 To: Multiple recipients of list ORACLE-L X-Comment: Oracle RDBMS Community Forum X-Sender: "Gogala, Mladen" Sender: root@fatcity.com Reply-To: ORACLE-L@fatcity.com Errors-To: ML-ERRORS@fatcity.com From: "Gogala, Mladen" Subject: RE: I/O contention with external process reading the oracle logs Organization: Fat City Network Services, San Diego, California X-ListServer: v1.0g, build 71; ListGuru (c) 1996-2001 Bruce A. Bergman Precedence: bulk Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit If your redo log files are normal unix files (i.e. not raw devices or Veritas quick I/O files, then the first process to read a block will bring that block into the buffer cache. The second process will find already in the cache, which might benefit the other guy. I/O contention seems unlikely. Running into an insufficiently qualified support person, on the other hand, seems very likely. You can always use replication to copy things to another instance. > -----Original Message----- > From: johanna.doran@sungard.com [mailto:johanna.doran@sungard.com] > Sent: Thursday, June 06, 2002 10:32 AM > To: Multiple recipients of list ORACLE-L > Subject: RE: I/O contention with external process reading the oracle > logs (online redo logs) > > > NB_ RESENDING in plain text - sorry, Outlook keeps seinding > in html no matter what default i set! > Hi lists, > > I am using Quest Shareplex product for Oracle to Oracle > one way replication. I have two systems (source and target) > and two environments (dev, demo). On system one, the > environments are setup as schemas within one oracle instance > (therefore each schema will be a SOURCE in the replication). > My other system has each environment set up a separate Orace > Instances (therefore each instance will become a TARGET in > the replication). > > I am trying to configure 2 separate replication streams > (ie so that each replication process is SEPARATE from the > other - one for DEV and one for DEMO). I will accomplish > this by setting up Shareplex to use mulitple processes. > > HOWEVER, Quest technical support has told me that this > will cause contention. However, I dont see why is would from > an os/oracle point of view. Basically Shareplex has a > process which reads the online redo logs......... tech > support is suggesting that is there a two processes trying to > access the same block in the logs that contention can occur. > This does not make sense to me. Below is the blurb from > techincal support when I questioned their initial repsonse: > > ************************************************************** > *************************************************************** > The reason you might run into a contention is because > multiple captue processes may be reading the same data block > in the redo log. Since there is only one process that can > access a single block, the other process may have to wait. > Contention is a possibilty, and you will need to run some > bench marks to find out how much, if any, contention you will have. > ************************************************************** > *************************************************************** > > I would find it HARD to believe that only ONE process can > read a block at a time. If this were true, then OLTP system > would FAIL miserably! > > Anyone have any ideas/comments regarding the OS and Oracle > interaction .... I mean are not the logs at this pointa UNIX > file? and can't multiple processes read a single unix file > without bringing the whole system to its knees? > Also, I am NOT knocking the techincal support, but I believe > that the opinion was formulated on an incorrect assumption on > the operating system and Oracle. > Thoughts/comments? > > Thanks in advance. > > Hannah > > > > > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.com > -- > Author: > INET: johanna.doran@sungard.com > > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 > San Diego, California -- Public Internet access / Mailing Lists > -------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: ListGuru@fatcity.com (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Gogala, Mladen INET: MGogala@oxhp.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru@fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).