RE: DBA assessment - slightly OT

From: Christopher Spence <cspence_at_FuelSpot.com>
Date: Wed, 26 Sep 2001 11:06:58 -0700
Message-ID: <F001.00399A3E.20010926105026@fatcity.com>

Wasn't planning on it, but here is a quick run down kind of a zoo today.

What is the difference between a lock and a latch?

Lock is generally used to do read consistency where latches are used for internal memory structures of Oracle. Locks have a queue where as latches do not, in short latches are simpler, and faster.

2. Explain what spinning is and why is it necessary?

Spinning is what is down when waiting for a latch, seeing as the latch should only be held for a short period of time, it is generally faster to spin or consume a small amount of cpu cycles and then request it ms later than giving up the process and doing a context switch only to have to get back on the cpu later. It is basically the time Oracle will wait for a latch, in theory, this should be very few ms or less.

3. What is the PL/SQL catch all exception called?

When others

4. Where would you "read" about a deadlock that occurred?

Alert log

5. How would you verify your data files you just backed up are not corrupt?

Dbv

6. Explain what two significant things that occur when you do a BEGIN BACKUP on a tablespace.

SCN on the file gets frozen, full redo blocks are written to log files rather than old and new information.

7. Explain the use of DECODE function.

Basically an if statement, very useful in SQL statements to implement some minor procedural logic.

8. What is a correlated sub query?

When the sub query refers to the parent query

9. Explain the "snapshot too old" error, and when does it commonly occur.

Snapshot too old means a process is going to the rollback segments to get a read consistent view of a block which has been over written, generally this happens on long running reports while a lot of changes are taking place.

What three powerful Oracle tuning tools require timed_statistics?

        Statspack
        Bstat/Estat
        Wait Event views

"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."

Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275

Fuelspot
73 Princeton Street
North, Chelmsford 01863

-----Original Message-----
Sent: Wednesday, September 26, 2001 2:26 PM To: Multiple recipients of list ORACLE-L

Hi Christopher,

So, are you going to tell the list what the answers are so that those that don't know can benefit.

Martin

-----Original Message-----
Sent: 26 September 2001 16:46
To: Multiple recipients of list ORACLE-L

What is the difference between a lock and a latch?
Explain what spinning is and why is it necessary?
What is the PL/SQL catch all exception called?
Where would you "read" about a deadlock that occurred?
How would you verify your data files you just backed up are not corrupt?
Explain what two significant things that occur when you do a BEGIN BACKUP on a tablespace.
Explain the use of DECODE function.
What is a correlated sub query?
Explain the "snapshot too old" error, and when does it commonly occur.
What three powerful Oracle tuning tools require timed_statistics?

These are off the top of my head, I had a nice drawn up list I spent more time on, but it is at home I think.

HTH, "Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."

Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275

Fuelspot
73 Princeton Street
North, Chelmsford 01863

-----Original Message-----
Sent: Wednesday, September 26, 2001 10:30 AM To: Multiple recipients of list ORACLE-L

If you were to choose 10 questions to evaluate the competency of a DBA what would they be given that the result would be their competence would be rated as of the following:

TERRIBLE (I would not let them within 100 miles of a database)
FAIR (I'd show them some basic admin, but do it myself, they've a lot to learn yet)
GOOD (I'd let them do some basic admin stuff by themselves but monitor their performance regularly)
VERY GOOD (I'd let them handle practically all admin type work and mentor them as required)
EXCELLENT (Hell, they could teach me a trick or too!)

Sean :)

Data Base Administrator
Oracle 7.3.3, 8.0.5, 8.1.7 - NT, W2K
[0%] OCP Oracle8i DBA ---> End 2002 deadline =:-O [0%] OCP Oracle9i DBA

-------------------------------- ------------

Organon (Ireland) Ltd.
E-mail: sean.oneill_at_organon.ie [subscribed: Digest Mode]

Visit: http://groups.yahoo.com/group/Oracle-OCP-DBA

"Nobody loves me but my mother... and she could be jivin' too." - BB King

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Author: Christopher Spence
INET: cspence_at_FuelSpot.com

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