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Serious Serious
Reported By: Raul Sinimae
Reported On: 9/21/2016
For: Version 4.43 Build 2
# 4435 Using Strict Change Detection Can Cause #8965 Index Buffer Corrupt Errors when Adding Filters

Our software is a Client/Server model with following setup:

- our server running on the server system accessing DBISAM files direct
- DBSRVR instance(s) running on the same server (accessing the same DBISAM files direct)
- remote client using remote sessions to get to data (using the DBSRVR listed above)
- Everything is dbisam 4.42 build 2.

One more thing to note is that in terms of data access new records are added by the remote client(s) but the server is constantly querying the tables for new/updated data (our software is notification/workflow solution so it needs to poll and see if there is new work to be done. this is almost continuous on server side. server is using mostly dbisam queries but in some cases might be using table component if it's basically "loop thru table" logic).

At this customer site we are getting semi-regular "DBISAM Engine Error # 8965 Index page buffers corrupt in the table 'CALLPNT'." on the server - "callpnt".

It's not easily reproducible and so far is happening about a twice a week. The only thing common is that in both cases they were using our remote client to make changes (however they have also been able to make changes without this error popping up).

In one case the error was happening for about 2 minutes and then went away by itself. Second time they had it for about 20 minutes and then just rebooted the server and of course it was fine after.

There does not appear to be anything wrong with any of the tables table - we've run verify and repair, including index rebuild and it all passes with flying colours.

Comments Comments
The issue was with the strict change detection setting not properly checking for changes/read locking the table when adding a filter and using some count probes into the indexes to get the optimization level of the filter.

Resolution Resolution
Fixed Problem on 9/30/2016 in version 4.43 build 3

Products Affected Products Affected
DBISAM Additional Software and Utilities
DBISAM ODBC Client-Server
DBISAM ODBC Client-Server with Source
DBISAM ODBC Standard with Source
DBISAM VCL Client-Server
DBISAM VCL Client-Server with Source
DBISAM VCL Standard with Source