17.10 - About System and AMP Outages During Compression - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - Database Design

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Published
July 2021
Language
English (United States)
Last Update
2021-07-27
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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.