Performance Tuning - Question 050

Which of the following are not tuning goals for undo segment management?

A . No transaction should ever run out of undo segment space.

B. Undo segments should never wrap during normal operation.

C . Readers should always see the read-consistent images they need.

D . Transactions should never wait for access to undo segments.

E . Undo segments should never extend during normal operation.

Explanation:

Answer B: Wrapping is expected and a normal operation. Each of the other answers are valid undo tuning goals. Transactions should never wait for access to undo segments and they should never run out of undo space; undo segments should not dynamically extend, and readers should always see the read-consistent view that they require for their application. Unnecessary waits can be remedied with more undo segments. Space issues can usually be resolved by adding more space to the undo tablespace. Dynamic extension, in a manually configured undo environment, is controlled by properly setting the extent size and optimal number of extents. Read-consistency issues can usually be resolved by adding more space to rollback segments, adding more rollback segments, or by increasing the UNDO_RETENTION parameter.