Block-level compression is fault-tolerant:
- If an AMP is down, the Ferret COMPRESS and UNCOMPRESS commands can still operate.
- If a database restart occurs when a table is being compressed or uncompressed, the interrupted operation completes during system recovery.
To see the compression or uncompression operations in progress during a system recovery after a database restart, use the Ferret command SHOWAMPRECOVERYBLC. You can also use that command to cancel the operations you just viewed if you want to minimize transaction recovery time after a restart.
- Compress and uncompress operations that are canceled during recovery via the SHOWAMPRECOVERYBLC command will remain in a mixed compressed and uncompressed state. Run the Ferret COMPRESS or UNCOMPRESS command again to make the table state consistent.
- If a database restart occurs when all database tables are being compressed or uncompressed, the interrupted operation completes only on the table in-progress at the time of the restart.