Enabling block-level compression at the system level allows you to enable block-level compression for individual tables. To accomplish this, use the optional BLOCKCOMPRESSION =block_compression_option clause for the statements CREATE TABLE, ALTER TABLE, and CREATE JOIN INDEX.
For Object File System tables, BLOCKCOMPRESSION has a default setting that you cannot change.
The valid specifications for block_compression_option in these statements are:
| DDL Statement BLOCKCOMPRESSION Keywords | Result |
|---|---|
| MANUAL | Table data is not compressed except when you specify a query band option to compress the table. The system is configured with BLC enabled for specific tables or table types. |
| AUTOTEMP | Table data is compressed or decompressed automatically based on the data temperature. |
| ALWAYS | Data for the table is compressed, even if query band options or system settings indicate otherwise. |
| NEVER | The table is never compressed, even if query band options indicate otherwise. |
| DEFAULT | System settings determine whether the table is manually, automatically, or never compressed. A table set to DEFAULT can be affected by any future change to the system default setting. |