20 July 2011 Discussion

20 July 2011 Discussion
1)Password file:-
In order to create password file in oracle we use a orapwd utility.Password file is an optional file.This file is used to create password for super users like sys and system which having sysdba and sysopera privilage.Normal user can by default part of the password file if we grant sysdba and sysopera privilage to the user.The orapwd utility uses a internal complex algorithim which conver the password into very complex formate, so it is very difficult to crack the password.

2)ORA-12514: TNS: Listener does not currently know of service requested in connect descriptor

Solution:-
A)Add the service name in the tnsnames.ora file in order to recognise the service
B)If it is already present and still it is not able to recognize the userid and passwrod.Then do a os authenitcation.

$sqlplus / as sysdba
$startup
This will start the database and may be the database is shutdown due to the shutting down of the server
C)Check the connection descriptore for service name
D)check which service the listner is currently recognising
E)Check the listner.log file for getting more clue on the error

3)What is the standard procedure to kill a process in oracle?
A:- First check the oracle process from the db end and then from the OS end and then kill at both end.
DB site:-

alter system kill ;
check the process is killed or not.

OS site:-
kill -9

4)CKPTR Process:-
Ans:- CKPTR stands for check pointer.This is a mandatory background process.CKPTR process trigger the DBWR to write the dirty buffer to the datafile.Ther are certain condition at which check point occur.


5)How tablespace occupy the space from operating disk?
Ans:- When tablespace is created with certain space  oracle will first create empty oracle blocks in the space. This blocks will be be used when data is inserted or utilized by the oracle.

6)What is the process of Update statement.

Ans:-

When update statement is fired it first performs the select statement then made the modification to the block.In the update statement oracle will search for the block in the database buffer cache.If it found then it will make changes to this block.If it doesnot find then it will retrive the block from database and made the change and keep a copy in the database buffer cache.


7)What is the process of insert statement?
Ans:- Insert statement will directly fetch free block from database and  made the changes and keep a copy in the buffer cache.

8)What is the structure of Oracle Block?
Ans:-Oracle block consists of 3 section.Data header,free section and data section.The data header contains the block information,free section is used for any kind of modification in future and data section will contain the actual data.

9)What are the mandatory parameters in the pfile?

Ans:-
db_block_size
db_name
sga_target
control_files
undo_tablespace
uddo_management

10)ORA-01092:Oracle instance terminated and disconnected forcefully
Ans:-
Solution:-
Check the alert.ora log file from bdump location(background_dump_dest).This will give you clear idea.
Probable reasons:-
a)Bad permission to BDUMP,UDUMP,ADUMP,CDUMP directory
b)Missing datafile name
c)a shutdown abort
d)Improper naming files when oracle is down or during database creation