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RE: standby config --> FAL_SERVER / FAL_CLIENT

From: <>
Date: Wed, 11 Feb 2004 10:07:08 +0530
Message-ID: <10898BE7CA96D611988B000802255AAF0503A34C@fmgrt>

Hi Jonathan,

        Thanks for highlighting the same. I have one question on this and hope = you would help me out. This factor of three as I understand is that if a = normal commit takes a factor time/wait? Pls explain) of x then maximum = protection mode would be a factor of 3x.=20

Also this 3x factor is for a single standby instance and would increase = 3x times for every additional setup of standby databases. Is my = understanding correct?

Best Regards

Sriram Kumar

-----Original Message-----

From: Jonathan Lewis []=20 Sent: Wednesday, February 11, 2004 1:45 AM To:
Subject: Re: standby config --> FAL_SERVER / FAL_CLIENT

Just clearing up a point on Maximum Protection and the meaning of "(does not wait till its applied)".

Isn't this the option where lgwr has to wait for confirmation that the redo has been written=20 into the standby log on the standby database=20 before writing to the online log on the primary=20 and acknowledging the commit.

One thing to watch out for with standby and this option is the effect on commits within=20 pl/sql calls. Oracle does not wait for sync if you issue a commit inside a pl/sql call,=20 issuing only one log sync write at the end=20 of the call - but if you switch to maximum protection, then every commit inside the call becomes a log sync call, and performance get much
worse. (I've had one report of a factor of three for a piece of code doing lots of commits inside a pl/sql loop).


Jonathan Lewis

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Hi Prem,

Yes there is a performance overhead with maximize protection. As I said = =3D
earlier, the LGWR process is going to ship the log changes to the =3D standby database (does not wait till its applied) and hence It boils =3D down to the network connectivity that exists between the primary and the = =3D
standby database. Your overhead is proportional to the network =3D bandwidth. Pls test it with a real load before you put in production.

Best Regards

Sriram Kumar

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Received on Tue Feb 10 2004 - 22:37:08 CST

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