Oracle DBA Interview Questions Answers Explanation

Oracle Interview questions and answers are here which will help you to prepare for the interview.

1.Explain the difference between a hot backup and a cold backup and the benefits associated with each. - A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.

2.You have just had to restore from backup and do not have any control files. How would you go about bringing up this database? - I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.

3.What is different between TRUNCATE and DELETE?

The Delete command will log the data changes in the log file where as the truncate will simply remove the data without it. Hence Data removed by Delete command can be rolled back but not the data removed by TRUNCATE. Truncate is a DDL statement whereas DELETE is a DML statement.

4.What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

1000000

5.What is an UTL_FILE? What are different procedures and functions associated with it?

The UTL_FILE package lets your PL/SQL programs read and write operating system (OS) text files. It provides a restricted version of standard OS stream file input/output (I/O).
Subprogram -Description
FOPEN function-Opens a file for input or output with the default line size.
IS_OPEN function -Determines if a file handle refers to an open file.
FCLOSE procedure -Closes a file.
FCLOSE_ALL procedure -Closes all open file handles.
GET_LINE procedure -Reads a line of text from an open file.
PUT procedure-Writes a line to a file. This does not append a line terminator.
NEW_LINE procedure-Writes one or more OS-specific line terminators to a file.
PUT_LINE procedure -Writes a line to a file. This appends an OS-specific line terminator.
PUTF procedure -A PUT procedure with formatting.
FFLUSH procedure-Physically writes all pending output to a file.
FOPEN function -Opens a file with the maximum line size specified.

6.What are between database triggers and form triggers?

Database triggers are fired whenever any database action like INSERT, UPATE, DELETE, LOGON LOGOFF etc occurs. Form triggers on the other hand are fired in response to any event that takes place while working with the forms, say like navigating from one field to another or one block to another and so on.

7.What is OCI. What are its uses?

OCI is Oracle Call Interface. When applications developers demand the most powerful interface to the Oracle Database Server, they call upon the Oracle Call Interface (OCI). OCI provides the most comprehensive access to all of the Oracle Database functionality. The newest performance, scalability, and security features appear first in the OCI API. If you write applications for the Oracle Database, you likely already depend on OCI. Some types of applications that depend upon OCI are: 
· PL/SQL applications executing SQL
· C++ applications using OCCI
· Java applications using the OCI-based JDBC driver
· C applications using the ODBC driver
· VB applications using the OLEDB driver
· Pro*C applications
· Distributed SQL

8.What are ORACLE PRECOMPILERS?

A precompiler is a tool that allows programmers to embed SQL statements in high-level source programs like C, C++, COBOL, etc. The precompiler accepts the source program as input, translates the embedded SQL statements into standard Oracle runtime library calls, and generates a modified source program that one can compile, link, and execute in the usual way. Examples are the Pro*C Precompiler for C, Pro*Cobol for Cobol, SQLJ for Java etc.

9.What is syntax for dropping a procedure and a function? Are these operations possible?

Drop Procedure/Function ; yes, if they are standalone procedures or functions. If they are a part of a package then one have to remove it from the package definition and body and recompile the package.

10.How to check if application 11i System is Autoconfig enabled ?

Under $AD_TOP/bin check for file adcfginfo.sh and if this exists use adcfginfo.sh contextfile=<CONTEXT> show=enabled 
If this file is not there , look for any configuration file under APPL_TOP if system is Autoconfig enabled then you will see entry like

11.How to check if Oracle application 11i System is Rapid Clone enabled ?

For syetem to be Rapid Clone enabled , it should be Autoconfig enabled (Check above How to confirm if application 11i is Autoconfig enabled). You should have Rapid Clone Patches applied , Rapid Clone is part of Rapid Install Product whose Family Pack Name is ADX. By default all application 11i Instances 11.5.9 and above are Autoconfig and Rapid Clone enabled.

12.What is main concurrent Manager types.

# ICM - Internal Concurrent Manager which manages concurrent Managers
# Standard Managers - Which Manage processesing of requests.
# CRM - Conflict Resolution Managers , resolve conflicts in case of incompatibility.

13.What is US directory in $AD_TOP or under various product TOP's .

US directory is defauly language directory in Oracle Applications. If you have multiple languages Installed in your Applications then you will see other languages directories besides US, that directory will contain reports, fmx and other code in that respective directory like FR for France, AR for arabic, simplifies chinese or spanish.

14.Where is Concurrent Manager log file location.

By default standard location is $APPLCSF/$APPLLOG , in some cases it can go to $FND_TOP/log as well.

15.Where would I find .rf9 file, and what it dose ?

These files are used during restart of patch in case of patch failure because of some reason.

16.Where is appsweb.cfg or appsweb_$CONTEXT.cfg stored and why its used ?

This file is defined by environment variable FORMS60_WEB_CONFIG_FILE This is usually in directory $OA_HTML/bin on forms tier. 
This file is used by any forms client session. When a user try to access forms , f60webmx picks up this file and based on this configuration file creates a forms session to user/client.

17.What is Multi Node System ?

Multi Node System in Oracle Applications 11i means you have Applications 11i Component on more than one system. Typical example is Database, Concurrent Manager on one machine and forms, Web Server on second machine is example of Two Node System.

18.Can a function take OUT parameters. If not why?

yes, IN, OUT or IN OUT.