Using Filer to make repairs to certain areas of the file system requires knowledge of data structures related to the Teradata File System. Teradata Database allocates cylinders for data storage of two basic types:
Normal cylinders can be of two fixed sizes:
On systems that have been initialized to use large cylinders, small cylinders are still used to store WAL and DEPOT data.
On systems that have been initialized to use large cylinders, large cylinders store all data types except WAL and DEPOT.
Note: For 4 KB storage devices, Teradata Database treats 4 KB sectors as eight contiguous 512 byte sectors.
Teradata Database employs a directory structure known as the cylinder map. The map stores a list of all cylinders (small, large, and durable) on the system. Although it is unlikely, if one or more entries in the map becomes corrupted, Teradata Database cannot properly identify the corresponding cylinder types or whether they are large or small cylinders. For example, a durable cylinder can appear to the file system incorrectly as a set of normal cylinders with invalid data, or a set of contiguous small cylinders can appear a single large non-durable cylinder. Such situations result in file system errors.
Use the following approaches to repairing such problems, depending on the nature of the problem:
Alternatively, an attempt can be made to manually repair the first CI of the durable structure that was corrupted, such that it will again be recognized as a durable cylinder. Once the CI has been repaired, use the REBUILDMAP command to force the Teradata Database File System to again recognize the durable cylinder.
In either case, quit and restart Filer after the repairs. This restarts the file system with the newly repaired CIs, which allows verification of the repairs.
For more information on Filer commands related to cylinder repair, see “ASSIGN” on page 103, “BADLIST” on page 107, “INIT” on page 141, “PATCH” on page 166, “QUARLIST” on page 174, “REALLOCDUR” on page 178, and “REBUILDMAP” on page 181.