Home » Oracle » 1z0-062 v.2 » Which technique will move the table and indexes while maintaining the highest level of availability to the application?
You are the DBA supporting an Oracle 11g Release 2 database and wish to move a table containing several DATE, CHAR, VARCHAR2, and NUMBER data types, and the table’s indexes, to another tablespace.
The table does not have a primary key and is used by an OLTP application.
Which technique will move the table and indexes while maintaining the highest level of availability to the application?
A. Oracle Data Pump.
B. An ALTER TABLE MOVE to move the table and ALTER INDEX REBUILD to move the indexes.
C. An ALTER TABLE MOVE to move the table and ALTER INDEX REBUILD ONLINE to move the indexes.
D. Online Table Redefinition.
E. Edition-Based Table Redefinition.
Correct Answer: D
Explanation/Reference:
*Oracle Database provides a mechanism to make table structure modifications without significantly affecting the availability of the table. Themechanism is called online table redefinition. Redefining tables online provides a substantial increase in availability compared to traditional methods of redefining tables.
*To redefine a table online:
Choose the redefinition method: by key or by rowid
*By key—Select a primary key or pseudo-primary key to use for the redefinition. Pseudo-primary keys are unique keys with all component columnshaving NOT
NULL constraints. For this method, the versions of the tables before and after redefinition should have the same primary key columns. This is the preferred and default method of redefinition.
*By rowid—Use this method if no key is available. In this method, a hidden column named M_ROW$$ is added to the post-redefined version of thetable. It is recommended that this column be dropped or marked as unused after the redefinition is complete. If COMPATIBLE is set to 10.2.0 or higher, the final phase of redefinition automatically sets this column unused. You can then use the ALTER TABLE … DROP UNUSED COLUMNS statement to drop it.
You cannot use this method on index-organized tables.
Note:
*When you rebuild an index, you use an existing index as the data source. Creating an index in this manner enables you to change storagecharacteristics or move to a new tablespace. Rebuilding an index based on an existing data source removes intra-block fragmentation. Compared to dropping the index and using the CREATE INDEX statement, re-creating an existing index offers better performance.
Incorrect:
Not E: Edition-based redefinition enables you to upgrade the database component of an application while it is in use, thereby minimizing or eliminating down time.
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