In Oracle 7.0 to 7.2 The use of the ‘alter session set events ‘immediate trace name coalesce level ts# command is the easiest way to defragment contiguous free space fragmentation. The ts# parameter corresponds to the ts# value found in the ts$ SYS table. In version 7.3 the alter table space coalesce is best. If the free space isn’t contiguous then export, drop and import of the table space contents may be the only way to reclaim non-contiguous free space.

How can you tell if a table space has excessive fragmentation

If a select against the dba_free_space table shows that the count of a tablespaces extents is greater than the count of its data files, then it is fragmented.

You see the following on a status report:

redo log space requests 23, redo log space wait time 0 Is this something to worry about? What if redo log space wait time is high? How can you fix this Since the wait time is zero, no. If the wait time was high it might indicate a need for more or larger redo logs.

What can cause a high value for recursive calls? How can this be fixed

A high value for recursive calls is cause by improper cursor usage, excessive dynamic space management actions, and or excessive statement re-parses. You need to determine the cause and correct it By either relinking applications to hold cursors, use proper space management techniques (proper storage and sizing) or ensure repeat queries are placed in packages for proper reuse.

If you see a pin hit ratio of less than 0.8 in the e-stat library cache report is this a problem? If so, how do you fix it

This indicate that the shared pool may be too small. Increase the shared pool size.

If you see the value for reloads is high in the e-stat library cache report is this a matter for concern

Yes, you should strive for zero reloads if possible. If you see excessive reloads then increase the size of the shared pool.

You look at the dba_rollback_segs view and see that there is a large number of shrinks and they are of relatively small size, is this a problem? How can it be fixed if it is a problem

A large number of small shrinks indicates a need to increase the size of the rollback segment extents. Ideally you should have no shrinks or a small number of large shrinks. To fix this just increase the size of the extents and adjust optimal accordingly.

You look at the dba_rollback_segs view and see that you have a large number of wraps is this a problem

A large number of wraps indicates that your extent size for your rollback segments are probably too small. Increase the size of your extents to reduce the number of wraps. You can look at the average transaction size in the same view to get the information on transaction size.

In a system with an average of 40 concurrent users you get the following from a query on rollback extents:

ROLLBACK CUR EXTENTS
——————— ————————–
R01 11
R02 8
R03 12
R04 9
SYSTEM 4

You have room for each to grow by 20 more extents each. Is there a problem? Should you take any action

No there is not a problem. You have 40 extents showing and an average of 40 concurrent users. Since there is plenty of room to grow no action is needed.

You see multiple extents in the temporary table space. Is this a problem

As long as they are all the same size this isn?t a problem. In fact, it can even improve performance since Oracle won?t have to create a new extent when a user needs one.

Define OFA?

OFA stands for Optimal Flexible Architecture. It is a method of placing directories and files in an Oracle system so that you get the maximum flexibility for future tuning and file placement.

How do you set up your tablespace on installation

The answer here should show an understanding of separation of redo and rollback, data and indexes and isolation os SYSTEM tables from other tables. An example would be to specify that at least 7 disks should be used for an Oracle installation so that you can place SYSTEM tablespace on one, redo logs on two (mirrored redo logs) the TEMPORARY tablespace on another, ROLLBACK tablespace on another and still have two for DATA and INDEXES. They should indicate how they will handle archive logs and exports as well. As long as they have a logical plan for combining or further separation more or less disks can be specified.

What should be done prior to installing Oracle (for the OS and the disks)

Adjust kernel parameters or OS tuning parameters in accordance with installation guide. Be sure enough contiguous disk space is available.