Prevent Termination of c-treeACE from LRU Cache Miss Limitations

4 June 2009

Affected Builds: All V9 lines with build dates prior to 090602
Criteria: c-treeACE Server with DATA_LRU_LISTS or INDEX_LRU_LISTS configurations set greater than 1
Indications: Server crash after large number of cache misses

When a c-treeACE Server is running with the configuration options DATA_LRU_LISTS or INDEX_LRU_LISTS set greater than 1, after a large number (2^32, over 2 billion) data or index cache misses occur, the c-tree Server terminates with an unhandled exception. These options default to 4 in c-treeACE Version 9. Thus all c-treeACE Version 9 servers are susceptible to this situation. You can verify these options in the server startup information found in the server status log file, CTSTATUS.FCS.

When a cache page is required to hold a page that is not already in cache and multiple data or index LRU lists are in use, the data and index cache logic increments a variable used to calculate which data or index LRU list is to be used . However, the variable was declared as a signed long integer, and after 2^32 increments, became negative, resulting in a negative index offset for an array of data/index cache LRU list mutexes. Redeclaring the variables as unsigned long integers resolves this issue.

An immediate fix for anyone with potential to be affected by this Version 9.0 only issue is to directly specify DATA_LRU_LISTS 1 and INDEX_LRU_LISTS 1 in the c-treeACE configuration file (ctsrvr.cfg) to avoid this unhandled exception condition. You will need to restart your server to enable this configuration change.

FairCom customers on current maintenance can request an updated V9 c-treeACE line at any time. Please contact your nearest FairCom office should you have any concerns that you are impacted by this update.