Data loss on MaxDB after system crash

[Former Member]

I have a Solution Manager 4.0 SP2 system running on SLES 9, 64 bit hardware and MaxDB 7.6.00.35. Everything seemed to be OK until a few days ago. After offline backup the system didn't start anymore properly (log showed entires like "No license found for hardware ID", "Broken pipe in Module rslgsend" etc.). The backup procedure is controlled by a cronjob: stopsap, backup of files, startsap. Initially it looked like the system had restarted properly but surveillance showed that there were errors. We stopped it again and found out that there were still running processes under the <sys>adm user. We assumed they were zombies and deleted them using kill -9. Now the system started again without any problems - or that's what it looked like initally. Later I found out that more or less all data since the initial backup after installation (17.05.2007) was lost. Verification of the database doesn't show any corrupt structures (???). My assumption is that data was actually never really written to the database files but only cached in system memory (actually not much, just a bit of customizing and user data), no checkpoints set etc.. Did anyone else ever come across that problem and, if yes, is there any way to solve this issue permanently? Actually it's not the first time this happend: some time ago I had a 4.0 SP1 test system with the same problem when I tried to patch it. Back then I just thought I messed it up with the support packages and reinstalled it.

By the way: I didn't get anything useful out of SAPNet

Thanks in advance for any hint.

Cheers,

Andy

Message was edited by:

Andy Rohr

[markus_doehr2 · Accepted solution]

And to your second question about "data loss":

It's possible that your log area was full, the database was stuck (in Oracle terms this would be something like an "archiver stuck").

After your stopped/killed/reboot the system, the system did roll back until the latest successfully savepoint/checkpoint.

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Markus

[Former Member · Accepted solution]

Hi Markus,

OK - thanks a lot - i guess that explains my problem.

Cheers,

Andy

[markus_doehr2]

First, your assumption, that everything just get "cached", isn't true.

MaxDB writes a savepoint after several minutes (I think the default is 10 minutes), this means, that all dirty pages (those that were changed) are written to the disks.

If you use MaxDB one usually does the following after the installation:

- Backup of the database (logically, triggered by the database, not backing up database files)

- Configuration of the Log area and setting up a medium for automatic log backup

If you just shut down the system, back up the files on operating system level and restart the system, the database is not aware of a backup and thus you will have a filled DATA are or a full LOG area.

To enable automatic log, you need to have at least one backup done by the database.

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Markus