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Monday, April 21, 2008

Preparation for DBA Interview


Nobody can give us complete or most of questions about interview because it is like our school, college exam which we don't know what exact questions comes in.


For school, college exam we need to go through every books which related to exams topic same like any Interview not for DBA only we need to prepare our self and go through each and every topic related to Oracle Database.

So now question is change from Oracle DBA interview question TO How to prepare myself for DBA interview?

And now I explained how we can prepare our self for DBA interview.

1. First understand we are going for DBA interview means Database Administrator.

“A person who’s responsible to handle and maintain database called DBA”
Means DBA position is very Hard, though, sensitive and confidential.

We can divide Oracle DBA interview in Four Major part.
1. Oracle Database Administration
2. Oracle Database Backup & Recovery Administration
3. Oracle Database Performance Tuning
4. Oracle Database Advanced administration

1. Oracle Database Administration
1. How to install Oracle Database Software on Different platforms?

Above point include Oracle Database Server or Client installation on different flavor like LINUX/SORALIS/UNIX/WINDOWS etc. so whenever you are going for interview must go through each installation guide.

2. How to Create Database?
There is two option for create DATABASE.
1. DBCA or 2. MANUALLY

3. How to create tablespace?
In above point we can include TABLESPACE type, DATAFILE size or AUTOEXTEND option.

4. How to configure Oracle Client to connect to Oracle Server?
In Above point we need to create TNS_ENTRY for database client through NETCA tools.

5. Database User Management
In above point we need to do User Creation, Specific permission on database according user needs. User profile creation.

6. Database Security
In above point we need to do Database Auditing, User Logon, Logoff information.

2. Oracle Database Backup & Recovery Administration
1. What is your backup strategy for database backup?

It is depends on many factor.
1. Database size It is in MB, GB or TB
2. Database type It is OLTP or DSS
3. Database availability It is 24x7
So whenever we design backup strategy for database keeps in mind above points. Because Oracle Expert Mr. Tom kyte said “We can FIX everything except BAD DATABASE BACKUP”.

2. What is your backup method for database backup?
It is also depend on condition.
1. Backup Type COLD backup or HOT backup
2. Backup Method RMAN or USER MANAGED
3. Backup Interval Every Day, Every Week, Every Month.

Oracle Corp. recommended to use RMAN (server managed) backup method for database backup but we can also use USER MANAGED backup if applicable.
NOTE: Always RUN production database in ARCHIVELOG mode.

After set proper backup strategy now practice on database recovery because interviewer must ask question about recovery side.

“Database Recovery is depend on Database backup”
There are so many or different types of recovery so we can divide recovery area in following.

How many types of recovery we can perform?
1. When datafile is lost
2. when controlfile is lost
3. when online redolog file is lost

Above three files is most important file for database if we lost them then we needed to perform recovery.
1. We can perform recovery at DATABASE level when complete database is lost.
2. We can perform recovery at TABLESPACE level when tablespace is lost.
3. We can perform recovery at DATAFILE level when datafile is lost.
4. We can perform recovery at DATA BLOCK level when any block is corrupted.
5. We can Multiplex CONTROLFILE or REDOLOG file for protect against LOST.

And suppose still we lost all controlfile or redolog files then recovery depends on many conditions.

NOTE: Before going for interview must go through backup and recovery user guide.

3. Oracle Database Performance tuning administration
This is third big area where most of DBA questions come.

For database tuning we need years of experience. But we can start with bottom.
1. What is database background process like DBRW, LGWR, CKPT SMON, PMON etc? 2. What is database memory area means SGA or PGA size?
3. What are database activities?

For above question oracle providing same diagnostic tools
1. STATPACK or AWR report
2. Tkprof
3. SQL trace
4. AUTO TRACE

Above are same tool to use find out bottleneck of slow database performance so we must know below things about this tools
1. How to use?
2. How to understand?
3. How to use these tools to solve database performance issue.

Above question is simple but answer is difficult because answer want practical or years of experience in database.
Note: Search on Google or visit OTN site for starting.

4. Oracle Database advanced administration
Oracle Advanced Features
1. Data Guard
2. RAC system
3. Stream
4. Partitioning
5. ASM
6. Others

DBA interviewer should ask question above points but it is also depend on DBA position because above points will include in senior level position.

End of the story…
For Interview we need good knowledge about Oracle DB and Experience because if we read thousands of interview related questions without good knowledge or experience we can clear interview but can’t be become a good DBA.

8 comments:

Babu B said...

Dear Taj,

Fantastic article...

Good post. Keep it up

Regards
Babu

moozai said...

Hi

I read this post 2 times. It is very useful.

Pls try to keep posting.

Let me show other source that may be good for community.

Source: Interview preparation

Best regards
Jonathan.

Pooja said...

Dear Taj

Nice article.


Pooja pancholi

Mohammed Taj said...

Thank you everyone.

Taj

Krishna Kirity said...

Really Nice Article and Informative..Keep it up and also keep posting..

Krishna Kirity said...

really nice article..keep it up..keep posting

abdul qadir said...

good one dude.

Anonymous said...

Its really very useful.
Please keep posting..