Truncation Overview

Truncation operations fall into two categories. The first category is the truncation that is performed as part of the normal StorNext processing. The second category is the “space management” truncation policies that are run only when the disk usage reaches certain key points.

For each file system defined on the MDC, there must be an entry in the /usr/adic/TSM/config/filesystems file.

There are five variables specified for each file system:

1. Low-water mark (default value is 75%)
2. High-water mark (default value is 85%)
3. Min-Use mark (default value is 75%)
4. Min-Use enable (default is true)
5. Truncation enable (default is true)

If truncation is not enabled on a file system, no files residing within that file system will ever be truncated. If truncation is enabled on a file system, as files are stored to media they automatically become truncation candidates unless they are marked for immediate truncation. For more information, see Normal Truncation, Immediate Truncation, and Daily Truncation.

Thus, a file can be truncated during one these operations:

1. Immediately after store (only if policy class is configured)
2. Daily truncation
3. LoSpace truncation
4. Emergency relocation