When using the CLUSTER keyword, maintain a dictionary archive for the same databases, stored procedures, or tables. Cluster archiving improves archive and recovery performance of very large tables and simplifies specific AMP restoring of non-fallback tables.
A complete cluster archive can restore all databases, stored procedures, and tables if it includes:
- A dictionary archive of the databases, tables, or stored procedures
- A set of cluster archives
- A set of specific AMP archives (if archiving non-fallback tables and AMPs were offline during the cluster archive) so all data is contained in archive files
Create a dictionary archive whenever the tables in the cluster archive might be redefined.
Although it is necessary to generate a dictionary archive only once if tables are not redefined, make a dictionary archive regularly in case an existing dictionary archive is damaged.
If a cluster archive is created over several days and a table is redefined in that archive, create an all-AMPs archive of the changed tables. Otherwise, the table structure might differ between archive files.
When archiving journal tables, archive the saved subtable created by a previous checkpoint. Consequently, it is not necessary to use locks on the data tables that are using the journal table. The Teradata Database places an internal lock on the saved journal subtable to prevent a concurrent deletion of the subtable.
The following rules govern the CLUSTER keyword:
- The option is allowed only when archiving data tables.
- A dictionary archive must be performed before a cluster archive.
- If any AMPs in the clusters are offline, archive non-fallback tables from those AMPs when they are brought back online.
- Utility locks are placed and released at the cluster level.
The dictionary archive contains data stored in the dictionary tables of the Teradata Database for the different objects being archived. Do the following to ensure that the table data in the cluster archive matches the dictionary definition in the dictionary archive:
- Archive clusters on tables with definitions that never change.
- Create the dictionary archive immediately prior to the cluster archives, without releasing Teradata ARC locks. Then initiate a set of cluster archive requests covering all AMPs.
Do not archive database DBC in cluster archive operations. However, specifying DBC (ALL) is supported. In this case, database DBC is excluded automatically by Teradata ARC.