Informix, Logical recovery during startup takes long

Logical recovery during startup takes long

Author	Message
Peter Dzvonya #1 / 7	Logical recovery during startup takes long We stopped our Informix server (7.31.FC6) and started it again a bit later. The engine needed more than an hour to finish the logical recovery. It really rolled back one transaction and the only reason I can accept that this might have been a long one. Questions: 1. Is it a normal behaviour? In case it really had a relative long uncomplete transaction should it not have rolled it back at shutdown? 2. How can this be prevented? Let us suppose you have a half an hour time-window to do a quick maintenance at your productive engine, you shut Online down, and later you start it again. But your startup is delayed because it needs a long, long time to make the logical recovery. I mean it may be very difficult to explain your users... Many thanks for any reply. Regards Peter Dzvonyar SAP-Consultant R/3 BC ------ Here is the relevant part of the message log: .... 18:17:35 Checkpoint Completed: duration was 1 seconds. 18:17:36 Informix Dynamic Server Stopped. Tue Nov 7 20:06:51 2000 20:06:51 Event alarms enabled. ALARMPROG = /informix/Q12/etc/log_full_muell.sh' ..... 20:07:05 Informix Dynamic Server Initialized -- Shared Memory Initialized. 20:07:05 Physical Recovery Started. 20:07:06 Physical Recovery Complete: 0 Pages Restored. 20:07:06 Logical Recovery Started. 20:17:21 Checkpoint Completed: duration was 5 seconds. 20:59:59 Checkpoint Completed: duration was 6 seconds. 21:23:11 Logical Recovery Complete. 0 Committed, 1 Rolled Back, 0 Open, 0 Bad Locks
Wed, 18 Jun 1902 08:00:00 GMT

Tony Flahert #2 / 7	Logical recovery during startup takes long Can you give us some more to go on. the $ONCONFIG, hardware info and the size of the instance. -- Tony Flaherty Snr. A/P, Informix DBA, HpUx Admin, Gimmi a broom! MFS Ltd. Quote: >We stopped our Informix server (7.31.FC6) and started it again a bit >later. The engine needed more than an hour to finish the logical >recovery. It really rolled back one transaction and the only reason I >can accept that this might have been a long one. >Questions: >1. Is it a normal behaviour? In case it really had a relative long >uncomplete transaction should it not have rolled it back at shutdown? >2. How can this be prevented? Let us suppose you have a half an hour >time-window to do a quick maintenance at your productive engine, you >shut Online down, and later you start it again. But your startup is >delayed because it needs a long, long time to make the logical recovery. >I mean it may be very difficult to explain your users... >Many thanks for any reply. >Regards >Peter Dzvonyar >SAP-Consultant R/3 BC >------ >Here is the relevant part of the message log: >.... >18:17:35 Checkpoint Completed: duration was 1 seconds. >18:17:36 Informix Dynamic Server Stopped. >Tue Nov 7 20:06:51 2000 >20:06:51 Event alarms enabled. ALARMPROG = >/informix/Q12/etc/log_full_muell.sh' >..... >20:07:05 Informix Dynamic Server Initialized -- Shared Memory >Initialized. >20:07:05 Physical Recovery Started. >20:07:06 Physical Recovery Complete: 0 Pages Restored. >20:07:06 Logical Recovery Started. >20:17:21 Checkpoint Completed: duration was 5 seconds. >20:59:59 Checkpoint Completed: duration was 6 seconds. >21:23:11 Logical Recovery Complete. > 0 Committed, 1 Rolled Back, 0 Open, 0 Bad Locks
Wed, 18 Jun 1902 08:00:00 GMT

smooth #3 / 7	Logical recovery during startup takes long Quote: >Can you give us some more to go on. the $ONCONFIG, hardware info and the >size of the instance. >-- >Tony Flaherty >Snr. A/P, Informix DBA, HpUx Admin, Gimmi a broom! >MFS Ltd. >>We stopped our Informix server (7.31.FC6) and started it again a bit >>later. The engine needed more than an hour to finish the logical >>recovery. It really rolled back one transaction and the only reason I >>can accept that this might have been a long one. >>Questions: >>1. Is it a normal behaviour? In case it really had a relative long >>uncomplete transaction should it not have rolled it back at shutdown? Depends how the engine was shutdown onmode -yuk and waiting for the engine to completely die it the correct way. Check the FAQ at www.smooth1.demon.co.uk Quote: >>2. How can this be prevented? Let us suppose you have a half an hour >>time-window to do a quick maintenance at your productive engine, you >>shut Online down, and later you start it again. But your startup is >>delayed because it needs a long, long time to make the logical recovery. >>I mean it may be very difficult to explain your users... Make sure no long transactions are active before shutting down. I think there is something in the FAQ about checking how much of the logical logs are currently in use. - Hide quoted text - - Show quoted text - Quote: >>Many thanks for any reply. >>Regards >>Peter Dzvonyar >>SAP-Consultant R/3 BC >>------ >>Here is the relevant part of the message log: >>.... >>18:17:35 Checkpoint Completed: duration was 1 seconds. >>18:17:36 Informix Dynamic Server Stopped. >>Tue Nov 7 20:06:51 2000 >>20:06:51 Event alarms enabled. ALARMPROG = >>/informix/Q12/etc/log_full_muell.sh' >>..... >>20:07:05 Informix Dynamic Server Initialized -- Shared Memory >>Initialized. >>20:07:05 Physical Recovery Started. >>20:07:06 Physical Recovery Complete: 0 Pages Restored. >>20:07:06 Logical Recovery Started. >>20:17:21 Checkpoint Completed: duration was 5 seconds. >>20:59:59 Checkpoint Completed: duration was 6 seconds. >>21:23:11 Logical Recovery Complete. >> 0 Committed, 1 Rolled Back, 0 Open, 0 Bad Locks
Wed, 18 Jun 1902 08:00:00 GMT

Rudy Fernande #4 / 7	Logical recovery during startup takes long Quote: > We stopped our Informix server (7.31.FC6) and started it again a bit > later. The engine needed more than an hour to finish the logical > recovery. It really rolled back one transaction and the only reason I > can accept that this might have been a long one. > Questions: > 1. Is it a normal behaviour? In case it really had a relative long > uncomplete transaction should it not have rolled it back at shutdown? > 2. How can this be prevented? Let us suppose you have a half an hour > time-window to do a quick maintenance at your productive engine, you > shut Online down, and later you start it again. But your startup is > delayed because it needs a long, long time to make the logical recovery. > I mean it may be very difficult to explain your users... One could always get into a situation like this because irrespective of whether Informix rolls back the transaction during shutdown or during "fast recovery" at startup, the time taken is (largely) dependent on the size (in terms of logical log rows) of the "Open" transaction. You could get some clue to the time that the shutdown/startup is going to take by determining (before shutting down), the earliest log used by the current open transactions and comparing it to the current log. Try select logbeg, nlocks from sysmaster:systxptab where logbeg > 0 order by logbeg; or retrieving it using the "onstat -x" command. If you find one which appears to use a large amount of log space, you could kill it before-hand (if you have the guts), or caution your users about the possibility of the delay. Rudy
Wed, 18 Jun 1902 08:00:00 GMT

Murray Woo #5 / 7	Logical recovery during startup takes long Peter 1. Not normal for most cases. However if you stop the engine with a very long transaction in progress, without first completing that transaction, then at startup the engine rolls the transaction back. This may take some time. I have seen a case of over 3 hours - but I was aware of a huge transaction involving temp tables of hundreds Mb. 2. Dont shut down with a big transaction in progress. MW Quote: -----Original Message----- Sent: Thursday, November 09, 2000 1:58 AM Subject: Logical recovery during startup takes long We stopped our Informix server (7.31.FC6) and started it again a bit later. The engine needed more than an hour to finish the logical recovery. It really rolled back one transaction and the only reason I can accept that this might have been a long one. Questions: 1. Is it a normal behaviour? In case it really had a relative long uncomplete transaction should it not have rolled it back at shutdown? 2. How can this be prevented? Let us suppose you have a half an hour time-window to do a quick maintenance at your productive engine, you shut Online down, and later you start it again. But your startup is delayed because it needs a long, long time to make the logical recovery. I mean it may be very difficult to explain your users... Many thanks for any reply. Regards Peter Dzvonyar SAP-Consultant R/3 BC ------ Here is the relevant part of the message log: .... 18:17:35 Checkpoint Completed: duration was 1 seconds. 18:17:36 Informix Dynamic Server Stopped. Tue Nov 7 20:06:51 2000 20:06:51 Event alarms enabled. ALARMPROG = /informix/Q12/etc/log_full_muell.sh' ..... 20:07:05 Informix Dynamic Server Initialized -- Shared Memory Initialized. 20:07:05 Physical Recovery Started. 20:07:06 Physical Recovery Complete: 0 Pages Restored. 20:07:06 Logical Recovery Started. 20:17:21 Checkpoint Completed: duration was 5 seconds. 20:59:59 Checkpoint Completed: duration was 6 seconds. 21:23:11 Logical Recovery Complete. 0 Committed, 1 Rolled Back, 0 Open, 0 Bad Locks
Mon, 28 Apr 2003 04:30:34 GMT

Peter Dzvonya #6 / 7	Logical recovery during startup takes long Quote: > You could get some clue to the time that the shutdown/startup is going to > take by determining (before shutting down), the earliest log used by the > current open transactions and comparing it to the current log. Try > select logbeg, nlocks from sysmaster:systxptab > where logbeg > 0 > order by logbeg; Thanks Rudy, that is what I looked for. With this query you have at least the chance to prepare yourself for a longer startup. But this case should occur very seldom: we have had Informix for 4 years and we have never had something like this. Quote: > If you find one which appears to use a large amount of log space, you could > kill it before-hand (if you have the guts), or caution your users about the > possibility of the delay. I suppose you have to use the "onmode -z" command. How can you identify the session to kill? What happens if you manually cancel the transaction? Is it cancelled immediately without any roll back? Thanks Peter --- Peter Dzvonyar SAP-Consultant R/3 BC
Wed, 18 Jun 1902 08:00:00 GMT

Rudy Fernande #7 / 7	Logical recovery during startup takes long Quote: > I suppose you have to use the "onmode -z" command. How can you identify the > session to kill? > What happens if you manually cancel the transaction? Is it cancelled > immediately without any roll back? onmode -z <session> will terminate the session "gracefully", rolling back all the changes it made. Note that this could take longer than if it were rolled back during a shutdown or fast recovery (because resources aren't dedicated to it). Here's a script that determines the session "occupying" the maximum log space. Its driven by the "onstat -x" command #!/bin/ksh # Extracts the following # 1. The earliest log with an open trx. # 2. The session information of the user who is running it EARLY_WARNING=100 OPENTRX=`onstat -x \| \ grep "^.............-" \| \ grep -v "^................................0" \| \ awk '{print $5, $3}' \| sort -n \| head -1` if [ "$OPENTRX" = "" ]; then echo No open transactions found. exit 0 fi set $OPENTRX EARLIEST_USED_LOG=$1 set `onstat -u \| grep $2 \| awk '{print $3, $4}'` CULPRIT_SESSION=$1 CULPRIT_USER=$2 CURRENT_LOG=`onstat -l \| grep "^.....................-C" \| awk '{print $4}'` LTXHWM=`onstat -c \| grep "^LTXHWM" \| awk '{print $2}'` NO_OF_LOGS=`onstat -l \| grep "\-.\-.\-" \| wc -l` LOGS_USED_BY_CULPRIT=`expr $CURRENT_LOG - $EARLIEST_USED_LOG` PROBLEM_THRESHOLD=`expr $NO_OF_LOGS \* $LTXHWM \* $EARLY_WARNING / 10000` clear echo " Earliest Log with Open Transaction : $EARLIEST_USED_LOG Current Log : $CURRENT_LOG Logs used by Culprit : $LOGS_USED_BY_CULPRIT User with Culprit Transaction : $CULPRIT_USER Session with Culprit Transaction : $CULPRIT_SESSION High Water Mark : $LTXHWM Percent Number of Logs : $NO_OF_LOGS Problem Threshold # of logs : $PROBLEM_THRESHOLD " if [ $LOGS_USED_BY_CULPRIT -gt $PROBLEM_THRESHOLD ]; then echo echo echo PROBLEMS AHOY!!! fi onstat -g sql $1 ###### End ##### Cheers Rudy
Wed, 18 Jun 1902 08:00:00 GMT

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