Compressing Tables, Databases, and Data Types Manually Using Ferret - Teradata Database

Compressing Tables, Databases, and Data Types Manually Using Ferret

Use the Ferret utility command COMPRESS to compress:

Data blocks of an existing table.

All tables in a database or all data of a particular type in a database (primary, fallback, CLOB primary, or CLOB fallback). Fallback data includes fallback secondary index subtables.

After a table is compressed, rows added to the table are compressed automatically. To uncompress the data blocks manually, use the Ferret command UNCOMPRESS.

To estimate the effects of the COMPRESS or UNCOMPRESS commands before you run them, use the ESTIMATE option. The output, which is based on sampling your data, shows the estimated block size and CPU usage that will result if you run the command.

Usage Notes

Teradata does not recommend using the Ferret COMPRESS/UNCOMPRESS commands on a table using temperature-based BLC because if the compressed state of the data does not match its temperature, the system may undo the commands.

If you use a COMPRESS command on a table specified as BLOCKCOMPRESSION=NEVER, the command is rejected.

For details on the Ferret COMPRESS and UNCOMPRESS commands, see Utilities.