Table of contents

Column-organized table variables

You use column-organized table variables to control the default behavior of a column-organized tables.

Important: These variables are only available from Db2® Version 11.5 Mod Pack 4 and later.
DB2_COL_STRING_COMPRESSION
  • Operating system: All
  • Default=UNENCODED_STRING:NO, Values: UNENCODED_STRING:YES
  • This variable lets you control whether Db2 can use the page-based string compression algorithms for string data.
  • Setting this variable to "UNENCODED_STRING:YES" will result in better compression for unencoded string data for new data insertion. However, it will also result in increased query application heap memory usage, and CPU utilization due to decompression.
  • Changes to this variable will not take effect until the database instance is restarted.
  • Existing tables will need to be unloaded and reinserted to take advantage of this feature. For instruction, see section 3 Best Practices to Compress Db2 Column-Organized Tables.
    Important: This is a fallback-incompatible feature. Setting this variable to "UNENCODED_STRING:YES" will cause tables in the database to be incompatible with any releases prior to Version 11.5 Mod Pack 4 because this feature changes the on-disk table structure. Falling back to any prior release after setting this variable to "UNENCODED_STRING:YES" may trigger a SQL1784N error when accessing column-organized tables.
DB2_COL_SYNOPSIS_SETTINGS
  • Operating system: All
  • Default=DEFER_FIRST_SYNOPSIS_TUPLE:NO, Values: DEFER_FIRST_SYNOPSIS_TUPLE: YES
  • This variable lets you control whether the first tuple of the synopsis table will be deferred or not.
  • Setting this variable to "DEFER_FIRST_SYNOPSIS_TUPLE:YES" will result in less storage space consumption from small tables.
  • Changes to this variable will not take effect until the database instance is restarted.
  • Existing tables will need to be unloaded and reinserted to take advantage of this feature. For instructions, see section 3 in Best Practices to Compress Db2 Column-Organized Tables.
    Important: This is a fallback-incompatible feature. Setting this variable to "DEFER_FIRST_SYNOPSIS_TUPLE:YES" will cause tables in the database to be incompatible with any releases prior to Version 11.5 Mod Pack 4 because this feature changes the on-disk table structure. Falling back to any prior release after setting this variable to "DEFER_FIRST_SYNOPSIS_TUPLE:YES" may trigger an assertion when working with any tables used before the fallback.