The percentage of storage space within a cylinder that AutoCylPack (automatic background cylinder packing) operations leave free of data, to allow for future table growth. This value for Free Space Percent (FSP) is used only for tables that do not have FSP otherwise specified.
10 through 75
Changes Take Effect
After the DBS Control Record has been written.
Free Space Percent (FSP) is the amount of space on a cylinder that is unoccupied and available for storage, expressed as a proportion of the total space on the cylinder. For tables that are expected to grow, free space on cylinders allows for table growth without requiring the additional cost of allocating free cylinders.
Teradata Database can maintain different levels of free space on cylinders used to store different tables. Static tables can be designated with little or no FSP, while tables that change and grow can be designated to have FSP levels that allow for table growth.
AutoCylPack runs periodically as a background task to maintain the set levels of FSP on table cylinders. If there is less than the desired FSP available on the cylinder, AutoCylPack moves some data to other cylinders to free up some space. If there is more than the desired FSP available on the cylinder, AutoCylPack moves data to the cylinder, potentially freeing up other cylinders.
A desired target level for FSP can be specified for tables in several ways. The FSP that AutoCylPack maintains for cylinders of each table depends on how the FSP was specified:
- If the FSP was specified in a CREATE or ALTER TABLE statement, AutoCylPack maintains that FSP for the cylinders of the table. If the FSP was specified in a CREATE or ALTER TABLE statement, and AutoCylPack is enabled, specifying a FREESPACEPERCENT value with a PACKDISK command is not recommended. In such cases, the FSP resulting from the PACKDISK operation would be temporary, and the table would be returned to the original table-level FSP setting by the background AutoCylPack task.
- If FSP was not specified with CREATE or ALTER TABLE, but PACKDISK was run on the table, AutoCylPack maintains the table cylinders at the FSP level that PACKDISK used.
- If an FSP was not specified in a CREATE or ALTER TABLE statement for the table, and PACKDISK was never run on the table, AutoCylPack uses the FSP specified by the AutoCylPackFSP field in DBS Control.