Purpose
Reserves a specified number of cylinders to be used only for permanent data storage.
Field Group
File System
Valid Range
1 through 524,287 cylinders
Default
10 cylinders
Changes Take Effect
After the DBS Control Record has been written.
Usage Notes
Free cylinders are used for permanent, spool, and temporary space in Teradata Database.
- Permanent (“perm”) space is used for storing data rows of tables.
- Spool space is used to hold intermediate query results or formatted answer sets for queries. Once the query is complete, the spool space is released as free cylinders.
- Temporary (“temp”) space is used for global temporary tables.
All requests for new cylinders are satisfied from the pool of free cylinders, so requests for perm cylinders compete with requests for spool and temp cylinders. If not enough free cylinders are available to meet a request, the request fails with a disk full error.
When the failed request involves perm cylinders, a lengthy rollback can be required, which adversely affects system performance. However, if the failed request involves spool or temp cylinders, very little rollback is generally required. Therefore, it is preferable to run out of spool and temp cylinders before running out of perm cylinders.
CylindersSavedforPERM reserves a number of free cylinders to be used only to fulfill requests for perm cylinders. If this number or fewer free cylinders is available, requests for spool and temp cylinders will fail, but requests for new perm cylinders will not fail unless there are no free cylinders available.