ORACLE DBA Interview Questions

ORACLE DBA Interview Questions 


Which process writes data from data files to database buffer cache?

Buffer cache ..........datafiles :dbwr
data files ...............buffer cache :server process




What is the use of control file

Control file contains: 
The database name
Names and locations of associated datafiles and redo log files
The time stamp of the database creation
The current log sequence number
Checkpoint information
Control file is back bone of database. Contorl file having all information about redo log files and log files.



What is difference between spfile and init.Ora file???

Spfile is in binary format we cannot edit but in init.ora file we can edit
Spfile is in binary format or in encrypted type we cannot modify the values but pfile is in ASCII format we can change the values.



Can you take online backup of a control file if yes, how?

SQL> ALTER DATABASE backup controlfile TO trace AS <PATH>
Specify the path where you want to store the controlfile backup.
We can do this by using RMAN:configure control file auto backup on;




diff between USER MANAGED ONLINE BACKUPS and RMAN BACKUPS

USER MANGED ONLINE BACKUPS are COLD BACKUPS
RMAN backups are normal BACKUPS


Do we need Licence for ORACLE DIAGNOSTIOC pack and TUNING PACKS

YES for some packs




How to check which component is avaliable and which feature is in aDATABASE

DBA_FEATURE_USAGE-STATISTICS view will display all the features and components list


How many default users will be created while using creating a database
32----SYS,SYSTEM,SCOTT,OUTLN,ADAMS,JONES,CLARK
,BLAKE,WOOD,STEEL,CLOTH,PAPAER,HR,OE,SH,DEMO,ANONYMOUS,
AURORA$ORB$UNAUTHENTICATEDAWR_STAGE,CSMIG,CTXSYS,DBSNMP,DIP,DMSYS,
DSYSS,EXFSYS,LBACSYS,MDSYS,ORACLE_OCM,ORDPLUGINS,
ORDSYSPERFSTAT,TRACESVR,TSMSYS,XDB



Can we drop unused users from the database..??
YES we can



DEFAULT passwords for SYS,SYSTEM users...???

SYS----CHANGE_ON_INSTALL or INTERNAL
SYSTEM----MANAGER


How to know which user has DBA privilege and which user ahs SYSDBA privilege

SYSDBA-----v$pwfile_users
DBA----------DBA_ROLE-PRIVS



How many control files is needed for the DB..???

min 2 max we can use many
but we have maintain in different lications for recovery purpose



If we lost the one control file, is there any effect on DB..???

YES......database wont come up even MOUNT mode also
we can restore the other controlfile to the same location of lost control file



if lost all the control files......how will u recover the database....???

we have to create a new controlfile withe all the DB structure options like size and paths of DB files and logfile limitations of datafiles and logfiles
then we have get the database in open mode and recover the database