dba interview questions

[shanthishanthi]

hai
this shanthi i am posting some dba interview questions pls post answers for this questions
What are things which play major role in designing the backup strategy?
What are RTO, MTBF, and MTTR?
What are the various tape backup solutions available in the market?
What is RAID? What is RAID0? What is RAID1? What is RAID 10?
What is the difference between physical and logical backups?
What is hot backup and what is cold backup?
When do you recommend hot backup? What are the pre-reqs?
How do you generate the begin backup script?
Give me the steps for recovering the full database from cold backup?
Give me the steps for TIME based recovery from the full database from hot backup. ?
Give me the steps for SCN based recovery from the full database from hot backup. ?
Give me the steps for CANCEL based recovery from the full database from hot backup. ?
Give me the steps for recovery with missing archived redo logs?
Give me the steps for recovery with missing online redo logs?
Give me the steps for recovery of missing data file?
Give me the steps for physical standby database creation?
What is db_recovery_file_dest ? When do you need to set this value ?
Give me the steps to perform the point in time recovery with a backup which is taken before the resetlogs of the db ?
Tell me about the steps required to enable the RMAN backup for a target database ?
What is the difference between obsolete RMAN backups and expired RMAN backups ?
What is recovery catalog ? Why do you need this ?
How do you install the RMAN recovery catalog ?
Can you skip specific tables when using RMAN DUPLICATE feature ?
What is FRA ? When do you use this ?
How do you clone the database using RMAN software ? Give me the brief steps ? when do you use crosscheck command ?
How do you setup the RMAN tape backups ?
How do you identify the expired,active,obsolete backups ? Which RMAN command you use ?
What is channel ? How do you enable the parallel backups with RMAN ?
What is auxiliary channel in RMAN? When do you need this ?
How do you identify what are the all the target databases that are being backed-up with RMAN database ?
Give me some of the RMAN catalog view names which contains the catalog information ?
What is oracle wallet ? Tell me about the encryption options available with RMAN ?
List atleast 6 advantages of RMAN backups compare to traditional hot backups ?
How do you identikit the block corruption in RMAN database ? How do you fix this ?
How do you verify the integrity of the image copy in RMAN environment ?
How do you enable the encryption for RMAN backups ?
What is backup set ?
What is the difference between cumulative incremental and differential incremental backups ?
How do you enable the autobackup for the controlfile using RMAN ?
What is configure command ? When do you use this ?
Give me the steps for setting up the physical stand by database with RMAN ?
Give me the steps for changing the DBID in a cloned environment ?
What is the significance of incarnation and DBID in the RMAN backups ?
What are the steps which needs to be performed in $ORACLE_HOME for enabling the RMAN backups with netbackup or TSM tape library software ?

[venugopal051984]

1. What are things which play major role in designing the backup strategy?
ans:1. How long is the allowable down time during recovery? - If short, you could consider using dataguard.

2. How long is the backup period? - If short, I would advise to use RMAN instead of user managed backup.

3. If limited disk space for backup never use user managed backup.

4. If the database is large you could consider doing full rman backups on a weekend and do a incremental backup on a weekday.

5. Schedule your backup on the time where there is least database activity this is to avoid resource huggling.

6. Backup script should always be automized via scheduled jobs. This way operators would never miss a backup period.

7. Retention period should also be considered. Try keeping atleast 2 full backups. (current and previous backup).
2>What are RTO, MTBF, and MTTR?
ans:RTO: Recovery Time objective-is the maximum amount of time that the database can be unavailable and still stasfy SLA's

MTBF (Meant tiem Between Failure)-

MTTR (Mean tie to recover)- fast recovery solutions
3>What is the difference between physical and logical backups?
ans:Logical backup means backing up the individual database objects such as tables, views , indexes.. using the utility called EXPORT, provided by Oracle. The objects exported in this way can be imported into either same database or into any other database. The backed-up copy of information is stored in a dumpfile, and this file can be read using another utility called IMPORT. There is no other way you can use this file.
Physical backups rely on the Operating System to make a copy of the physical files like data files, log files, control files that comprise the database
4>What is hot backup and what is cold backup?
ans: We take the hot back up when the database is in archive log mode and cold backup when the database is in no archive log mode.
5>When do you recommend hot backup? What are the pre-reqs?
ansatabase must be Archivelog Mode
Archive Destination must be set and LOG_ARCHIVE_START=TRUE (EARLIER VERSION BEFORE 10G)
6>How do you generate the begin backup script?
ans:SQL>set head off
SQL>spool beginbackup.sql
SQL>select 'alter tablespace ' tablespace_name ' begin backup;' from dba_tablespaces;
SQL>spool off
This will create file beginbackup.sql with entry for all tablespaces remove any unnecessary lines & then execute this script into SQL like
SQL>@beginbackup.sql
(Once you execute this script this will put all tablespaces in to begin backup mode)
Now create backup of your control file in Human Readable format like
alter database backup controlfile to trace as '/some/path';
You can reuse it by removing comment at beginning & replace them with connect / as sysdba
then Copy all your datafiles redo logs and control file from your database server to backup location.
After datafiles are copied don't forget to end backup for all tablespace
Here is the scripts
SQL>set head off
SQL>spool endbackup.sql
SQL>select 'alter tablespace ' tablespace_name ' end backup;' from dba_tablespaces;
SQL>spool off
This will create file endbackup.sql with entry for all tablespaces remove any unnecessary lines & then execute this script into SQL like
SQL>@endbackup.sql