IDS Forum

Re:LOGSIZE recommendation

Posted By: ART KAGEL, BLOOMBERG/ 731 LEXIN
Date: Thursday, 18 October 2007, at 12:24 p.m.

In Response To: LOGSIZE recommendation (GARY PRICE)

I agree that the size and number of logs need to be adjusted. Sizing is a trade off between safety on one hand and performance on the other. The smaller the log files the more frequently they will be archived (assuming that you are using continuous log backup or backing up logs using the ALARMPROGRAM as they fill). The larger the log files the less impact on the system.

The number of logs depends on three factors:
- The size of each logfile
- The size of an acceptable large/long transaction
- How much recovery data you will need to have on disk ready to recover

You should have enough logs (times log size) to allow a valid large transaction plus the expected other update volume that may happen in other sessions during that large transaction plus about 25 - 40%.

Art S. Kagel

----- Original Message -----
From: Gary Price <ids@iiug.org>
To: ids@iiug.org
At: 10/18 11:52:01

Hi.

I'm currently preparing to migrate our Informix databases to new servers in
the datacenter of our parent company. Also configuring an HDR pair for high
availability.

We've run some performance tests, including an application mass update. When
this test, and the nightly update cycle run, the logs offload about once every
1-2 minutes. This seems a bit excessive, however, I realize there is a
tradeoff in checkpoints/recovery time/data loss/sync'ing HPL, etc. So I
thought I'd ask for some recommendations from this group.

Current specifications are
LOGSIZE=2000
LOGFILES=10
LOGBUFF=32

Logs are offloaded via the alarmprogram.sh using ONBAR and Netbackup to a
virtual tape library, pretty quick.

Note that this database/application are from a 3rd party vendor who supplied
most of the database configuration parameters.

Thanks for your assistance

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Messages In This Thread

• LOGSIZE recommendation
  GARY PRICE -- Thursday, 18 October 2007, at 11:51 a.m.
  • RE: LOGSIZE recommendation
    Knox, Ernest -- Thursday, 18 October 2007, at 11:59 a.m.
  • RE: LOGSIZE recommendation
    Robert Roussey(IT) -- Thursday, 18 October 2007, at 12:22 p.m.
  • Re:LOGSIZE recommendation
    ART KAGEL, BLOOMBERG/ 731 LEXIN -- Thursday, 18 October 2007, at 12:24 p.m.
  • Re: LOGSIZE recommendation
    Kern Doe -- Thursday, 18 October 2007, at 12:28 p.m.

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