The Ferret SHOWCOMPRESS command has two new output display options that provide additional information about table data compression:
- /S displays the table ID's, table name and subtable ID's of the compressed and uncompressed tables.
- /L displays the compression state, compression algorithm, compression level, exact compression ratio, exact % of blocks, exact used GB, and exact % of data, in addition to the information provided by the /S option.
- The new /L display option allows you to determine exactly how much data in a table is compressed and uncompressed, and the exact compression ratio. (The related SHOWBLOCKS command provides only estimates based on a small sample of the table data.)
- Because the /L option displays the algorithm used to compress the data, you can:
- Validate that the correct algorithm has been used based on the data types of the table columns
- Compare the space-saving benefits of different compression algorithms
- SHOWCOMPRESS /L can require a long time for large systems, because it must traverse each data block to obtain exact compression statistics.
For more information on block-level compression, see Teradata® Database Design.