Hi Family.

Use it or lose it!  It's been a while since I configured an ONCONFIG file and there seem to be some new items in 14.10.  But I would tackle them one by one as it comes back to me.

So for starters: The default value for DYNAMIC_LOGS is 2 so that "The server adds a new logical log when necessary."  I had this in release 12 as well, if I recall correctly.  But a comment also describes parameter:
#AUTO_LLOG    - Add logical logs automatically to improve performance
This does not have a setting in the ONCONFIG.  So I have some questions:

1. For DYNAMIC_LOGS, when creating a new log, where does it create them?  I would guess in the ROOTDBS, although I have every intention of moving all logs out of root and into llogdbs and plogdbs (yet to be created).  With this in mind I would set DYNAMIC_LOGS to 1 (inform DBA) so that I control where new logs are created.

2. While AUTO_LLOG is not set in onconfig.std, I would set it to:
    AUTO_LLOG  1,llogdbs,15000

3. Now that I've suggested these settings, am I contradicting myself by setting both as described?

Lucky to have grabbed some 14.10 manuals in PDF; the online doc is a gluteal pain to search.

Thanks much for advice.  I'm taking this slow, since this laptop needs to be booted to Windows most of the time.

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Jacob Salomon
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Nobody goes there anymore, it's too crowded.  --Attr: Yogi Berra
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Jacob:

The third field of the AUTO_LLOG parameter is not the max size of  a single log but rather the maximum total size of all logical logs. It is a stopper to prevent the AUTO_LLOG from just going nuts and adding new logs forever, so the 15000 value is likely way too low. AUTO_LLOG and DYNAMIC_LOGS do not interact at all. DYNAMIC_LOGS always allocates new logs in the root dbspace. AUTO_LLOG uses the specified dbspace if there is room and uses chunk extension or the Storage pool if the specified dbspace fills up.

Art

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Art S. Kagel, President and Principal Consultant
ASK Database Management Corp.
www.askdbmgt.com
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Original Message:
Sent: 5/8/2023 6:11:00 PM
From: Art Kagel
Subject: RE: Difference between ONCONFIG parameters DYNAMIC_LOGS and AUTO_LLOG

Jacob:

The third field of the AUTO_LLOG parameter is not the max size of  a single log but rather the maximum total size of all logical logs. It is a stopper to prevent the AUTO_LLOG from just going nuts and adding new logs forever, so the 15000 value is likely way too low. AUTO_LLOG and DYNAMIC_LOGS do not interact at all. DYNAMIC_LOGS always allocates new logs in the root dbspace. AUTO_LLOG uses the specified dbspace if there is room and uses chunk extension or the Storage pool if the specified dbspace fills up.

Art

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Art S. Kagel, President and Principal Consultant
ASK Database Management Corp.
www.askdbmgt.com
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AUTO_LLOG would expand you log space if your load is so high, in relation to existing log space, that you're seeing more and maybe even blocking checkpoints.
 -> aim: performance, esp. in a auto-administered embedded environment

DYNAMIC_LOGS is meant for long transaction rollbacks only, to (try and) make sure the rollback will fit into your logs.
 -> aim: avoid system down (not block) from too big transaction rollback

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Andreas Legner
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Thanks Andreas.

That's a vital difference between the two parameters.  My solution to prevent a logs-full during a long transaction rollback was always to set LTXHWM=40 and LTXEHWM=45.  I think that was mathematically provable to prevent filling logs but I lack [the late] Brad Nohejl's skill in proving these things.  (Anyone remember Brad?)

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Jacob Salomon
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Nobody goes there anymore, it's too crowded.  --Attr: Yogi Berra
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Original Message:
Sent: Fri May 12, 2023 09:28 AM
From: Andreas Legner
Subject: Difference between ONCONFIG parameters DYNAMIC_LOGS and AUTO_LLOG

AUTO_LLOG would expand you log space if your load is so high, in relation to existing log space, that you're seeing more and maybe even blocking checkpoints.
 -> aim: performance, esp. in a auto-administered embedded environment

DYNAMIC_LOGS is meant for long transaction rollbacks only, to (try and) make sure the rollback will fit into your logs.
 -> aim: avoid system down (not block) from too big transaction rollback

------------------------------
Andreas Legner
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