FAQ
Sorry for the late reply,
thx a lot all of u for the help

Regards
Sameer
--- "Godlewski, Melissa"
wrote:
Sam,

Que1:
If you have statistics on the table then the cost
based optimizer is used.
If you have out of data statistics you could be
sending bad information to
the optimizer for join conditions. Using the
explain plan and plan table
(utlplan.sql in $oracle_home/rdbms/admin) will show
you cost information and
access paths to the data.

Que2:
The trace file should have a date time stamp that is
near the time you ran
yours. Additionally if you look at the trace file
it will have the osuer
information in it.

Que3:
It's hard to say the cause. You will need to look
at v$session and
v$session_wait to identify what the session in
waiting for. Is it possible
there was other jobs executing on the system which
slowed down your query
the second time? On NT the perfmon on UNIX top will
give you some
information. You need to know what the waits are.
Additionally you can
trace or dump the session.

Que4:
Run an explain plan and tk_prof on the session to
find out what objects the
application is using. Verify all the indexes are
there and not dropped
accidentally. You need to find the objects and
verify the access paths the
optimizer is using for the application are the best
ones. Hints or sql
rewrite may be in order.

Que5:
I'm not sure what you mean by logical backup. Maybe
below suggestions may
work.
Are you using RMAN for backups. If so look into
tablespace recover. If not
restore your backups to a development/test server
recover the tablespace and
associated data. Export/Import to your other
machine.


-----Original Message-----
From: sam d
Sent: Tuesday, June 11, 2002 9:24 AM
To: Multiple recipients of list ORACLE-L
Subject: Performance Tuning and Backup & Recovery


Hi,

I don't have much onhand experience, I thought
list is the appropriate place to get information.
These are related to Oracle Performance Tuning and
Backup & Recovery.

I have a system of Oracle 8i under HP-Unix and with
ARCHIVELOG on. It has been running and stable since
last 2-3 years. This was a brief overview.

Que 1: Assuming that I am using Cost based Optimizer
(CBO); I have a query which is a join of three
tables
out of which only one table have been analyzed and
in
first case rest two were analyzed but long time back
and after that I have changed the structure of the
table and in second case the other two tables have
not
been analyzed. Will Oracle use CBO ? I know it will
but then what will be the behavior of optimizer ?
Will
it take the best guess for the other two tables in
both the cases and if yes then those best guesses
will
be depending upon on what ?

Que 2: Suppose u have ran EXPLAIN PLAN for a
particular query at sqlplus prompt and there are
around 50 more users running EXPLAIN PLAN at the
same
time from the UNIX bos itself. In this case the
OSUSER, TERMINAL, PROGRAM will be same (u know it
better). Now suppose I want to run TKPROF against
the
trace file how will I identify which will be my
trace
file in USER_DUMP_DEST directory ?

Que 3: Supposing if I have Oracle Report running on
Oracle. I passed 3 parameters first time it took me
around 3 seconds to execute and 4 parameters second
time its hogging the system taking almost 25 minutes
to run. There are no concatenated indexs on the
underlying tables. What might be the cause and how
would u go about identifying it ?

Que 4: A user starts complaining about a particular
part of an appln. What will be my first steps to
optimize it ?

Que 5: Let's say we have a situation where at point
"A" I took a complete db backup. Somewhere after
point
"B" I lost an online redo log file. I recovered the
db
using the bck taken at point "A" and archived redo
log
files and started the new incarnation at point "B".
I
took a complete logical backup at point "B" and
taking
incremental backup after that. Now again at point
"C"
I took the complete bck. If I have dropped a
tablespace somewhere in between point B and C which
are the possible ways to recover it and which one
will
be the fastest ? (Of course if possible).

A---------------B---------------C---------------D

If I am not clear on any of the part please let me
know and I'll do the needful.

Thanks


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