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Teradata RDBMS Database Administration - NCR

NCR Teradata RDBMS Database Administration - NCR , 2004. - 616 p.
Download (direct link): teradatadatabaseadmin2004.pdf
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Chapter 8: Archiving, Restoring and Recovering Data

Arc Recovery versus FastLoad

Step Action
3 Submit the ROLLFORWARD RESTORED JOURNAL command to replace existing data table rows with their after-image rows stored in the restored journal.
4 Submit the ROLLFORWARD CURRENT JOURNAL statement to rollforward any changes made since the journal table was archived. This statement rolled forward the saved subtable first followed by the active subtable.

PRIMARY DATA Option

This option replaces only primary row images during the rollforward process. It ignores secondary index and fallback rows.

If you use this option with a rollforward operation, you can reduce the amount of I/O. It also improves the rollforward performance when recovering a specific AMP from disk failure.

Unique indexes are invalid when recovering a specific AMP. Always submit a BUILD statement when the rollforward command includes the PRIMARY DATA option.

Therefore, the PRIMARY DATA Option:

Ignores fallback rows and secondary index rows

Reduces amount of I/O

Improves performance when recovering single-AMP

ROLLFORWARD Restrictions

The following table illustrates important restrictions in using the ROLLFORWARD statement.

8 - 10

Teradata RDBMS Database Administration Chapter 8: Archiving, Restoring and Recovering Data

Arc Recovery versus FastLoad

ROLLFORWARD Restriction Description
AMP-specific Restore If you perform a restore operation on a specific AMP rather than on all AMPs, the ROLLFORWARD command does not permit you to use the TO CHECKPOINT NAME option. Following an AMP-specific restore, the system permits a rollforward only to the end of the journal. You must follow up the restore process with a rollforward of the entire journal table.
All-AMP Restore When you perform an all-AMP restore, you choose whether to submit the ROLLFORWARD command with the TO CHECKPOINT NAME option, or to the end of the journal. The PRIMARY DATA option of the ROLLFORWARD statement indicates that the operation should ignore secondary index and fallback rows that will reduce the amount of I/O during rollforward. If you use this option, follow up with the BUILD statement. Use the DBC.Events view to determine event numbers and/or checkpoint names.

For example:

SELECT EventNum FROM DBC.Events WHERE CreateDate = 940819; SELECT CheckPointName FROM DBC.Events WHERE CreateDate = 940819;

DELETE JOURNAL Statement

The DELETE JOURNAL command erases the contents of either the restored subtable or the saved subtable of a permanent journal. You must have the RESTORE privilege to execute this command.

You cannot delete:

Rows from an active journal.

A saved subtable when all the following conditions are true:

A CHECKPOINT statement in the archive utilized an access lock

The journal is not dual image

One or more AMPs are off-line and the saved subtable does not have a dual journal

Note: When a journal archive has all three of the above conditions, transactions between an all-AMP archive and a single-AMP archive may not be consistent.

8 - 10 Teradata RDBMS Database Administration

Chapter 8: Archiving, Restoring and Recovering Data

Arc Recovery versus FastLoad

Recovery Control Views

Several system views contain information about ARC utility events. You can use these views for recovery control.

This view Provides information about ... Table Name
DBC.Association objects (databases, users, tables, views, macros, indexes, stored procedures) that you imported from another Teradata RDBMS system or created via the Archive/Recovery COPY statement DBC.DBCAssociation
DBC.Events[X] archive/recovery activities, with a row (audit trail) for each archive and recovery event DBC.RCEvent
DBC.Events_Configuration[X] archive and recovery activities that did NOT affect all AMPs. DBC.RCConfiguration
DBC.Events_Media[X] archive and recovery activities that involved removable media DBC.RCMedia

Association View

The Association view allows you to retrieve information about an object imported from another Teradata RDBMS.

An existing object created with the ARC COPY command also appears in the Association view. If you later drop a copied object from its new destination, the information is deleted from the Association table and is no longer available.

The following example uses the Association view to list all tables, views, or macros that were copied into the payroll database.

The result of the query displays imported and current table names. The object column displays the current name of each table. The Source column provides the name of the original table. The event column shows the number assigned to the restore operation.

SELECT TRIM (DatabaseName)ll'.'llTableName (NAMED Object, FORMAT 1X (25)') TRIM (Original_DatabaseName)ll'.'ll Original_TableName (NAMED Source, FORMAT ~X(25)') EventNum (NAMED Event, FORMAT '9(5)') FROM DBC.Association WHERE DatabaseName LIKE %Payroll%' ORDER BY Object ;
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