common Oracle DBA interview questions and answer
Here is a small list of questions and answers for junior and mid-level Oracle DBA jobs. Mastery of these
questions and answers will help you survive most interview session, and also expose you to some basic and
advanced tips you need on the job.
What is the relationship between Control files and V$view?
V$views are kept in the control file. This is why v$ views are always accessible even when the database is in a
lesser state.
Can you access V$view while the database is not open?
Yes. V$view can be accessed even when the database is in nomount mode or in a lesser state.
How many stages are involved in getting the database open and running?
3 stages namely: Nomount, Mount and Open stage
What are the Mandatory processes in Oracle?
The processes are the backgound processes. The mandatory ones are Checkpoint, PMON, SMON, Log Writer
and Database Writer.
What is an instance?
A combination of memory structure and background processes.
Where can I monitor the Retore job that my colleague did to check if it went well or done properly?
Alert log. Alert log is in background dump. From SQL prompt issue: 'show parameter background dump'
I discovered that my control files are missing, what are my option?
Create another control file from the existing one (multiplex). If there is no existing one, create/build Control file
from scratch with a text file. Always back up control file to Trace so that you can have a text file to create a
fresh control file.
What is RAC?
Real Application Clusters. A combination of multiple instances accessing a database. The node represents
each instance in the cluster.
Why should a client use RAC?
To avoid a single port failure. When there is only one instance, reliability and fault tolerance is low.
What are the demerits of RAC?
It is expensive to maintain. It requires lot of resources (hardware and manpower) as well as maintenance costs.
Most firms now use VMware to reduce hardware costs.
What is ASM?
Automatic Storage Management
What would you use ASM?
It is free and more convenient for file management. It helps with load balancing as well as improves reliability
and availability.
What is the difference between full and incremental backup?
Full backup is when you backup the whole database and the database is not in open mode. Incremental
backup is when you copy the changes that has occured after the last full backup. This is usually done when the
database is open and running, and in ARCHIVELOG mode.
Can you use RMAN without database in archivelog mode?
Yes, you can take a cold backup when the database is cleanly shut down.
What is DATAPUMP?
It is a new features that oracle introduced to enhance import and export of database, tablespace, schema and
tables. Prior to Datapump, DBAs used regular imp and exp.
What are the basic features that differentiate Datapump from Import and Export?
Datapump allows remaping of database, tablespace, schema and tables. Datapump is also very fast. You can
increase parallelism by increasing the workers that will execute the job.
Please note that parallelism is only compatible with Enterprise edition of oracle 10g and 11g.