Unformatted text preview: e same disk
C. Tablespace containing a rollback segment
D. Different tablespaces on different disks
For better performance the ORDERS table and the ORDID_NDX index must be stored in
different tablespaces on different disks.
A: If these objects will be in the same tablespace it will cause performance degradation.
B: Different tablespaces on the same disk will still require extensive I/O operations contention,
because Oracle will try to retrieve index and data blocks from one disk device in one time.
C: It's not recommended to put data or index tablespaces on disk, where rollback segments are
located: it will cause I/O contention.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 844.
Chapter 18: Tuning Memory and Operating System Use
Which two statements about row migration are true? (Choose two)
A. Row migration is caused by a PCTREE value set too low.
B. Row migration can be resolved using the ANALYZE command.
C. Row migration can be reduced by choosing a larger block size.
D. Row migration means that row pieces are stored in different blocks.
E. Queries that use an index to select migrated rows perform additional I/O
Answer: A, B
Higher PCTFREE values represent a proactive solution to row chaining and migration. The
ANALYZE OBJECT_NAME LOST CHAINED ROWS INTO CHAINED_ROWS command is
used to determine whether there are chained rows in the database.
C: Row migration cannot be reduced by choosing a larger block size, because it's impossible to
predict size for all updates for rows.
D: Row migration occurs when a user process updates a row in an already crowded data block,
forcing Oracle to move the row out of that block and into another one that can accommodate the
row. Row chaining means that row pieces are stored in different locks. It happens when Oracle
attempts to migrate the row but cannot find a block large enough to fit the entire row, so it breaks
the row into two ore more parts and stores par...
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- Fall '09
- Oracle Database, Jason S. Couchman, DBA Certification Exam, Certification Exam Guide