Case study 21: How big tempdb should be?
  • Platform: HP-UNIX 11, Tru64 , Windows
  • Sybase ASE version: 12.5.x, 15.x
  • Background story: We have one table which is about 500MB big. When we tried to run update all statistics, we got an error that there is not enough space in data segment in tempdb database.
  • Task: Find out how much space must be designated for tempdb?
  • Solution: Doing small research on the internet gave me some results: tempdb should be initially set to on 20% to 25% of user database size. But if you have big tables which are bigger than space allocated for tempdb, tempdb have to be as big as the biggest table in database. It must be set to that size if you are doing update statistics on big tables.
    For Sybase ASE 15.x edition, clause sampling is introduced. It means that only some percent of whole table is going to be used for making statistics, instead of whole table. For more details, look at Reference Manual: Commands.

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