DBA

Location of Oracle Password hashes

* Database -sys.user$ -password
*Oracle Password File
*Data File of the system Tablespace
*(full) Export Files
*archive logs

Show oracle password hashkey

sql>select username,password from dba_users;

sql>select name,password from sys.user$ where password is notnull.

How to change an Oracle Password?

You should always use the pasword because the password is sent unencrypted over the net If you use the alter user syntax.

* alter user myuser identified bu my!supersecretpassword;

*grant connect to myuser identified by my!supersecretpassword

*update sys.user$ set password='F894844C34402B67' WHERE name='SCOTT';restart the database necessary

*sql*plus command:password or password username.

How to change an Oracle password temporarily?

In Oracle it is possible to change a password temporarily. This can be useful for DBA which act as a different user.

SQL> select username,password from dba_users where username='SCOTT';

USERNAME PASSWORD-------- ----------------SCOTT F894844C34402B67

SQL> alter user scott identified by mypassword;

Now login with the following credentials: scott/tigerAfter doing your work you can change the password back by using an undocumented feature called "by values"

SQL> alter user scott identified by values 'F894844C34402B67';

http://www.red-database-security.com/whitepaper/oracle_passwords.html

We can check the Database Created as 32bit Or 64bit Platform through below sql query


SQL> select metadata from sys.kopm$ ;METADATA
-----------------------------------------------------------0000006001240F050B0C030C0C0504050D0609070805050505050F05050505050A050505050504050607080823472323081123081141B023008300B207D00300000000000000000000000000000000000000000000000000000000000000000000000000


If above Colored Character Is "B023" means 32bit


Or
If it is "B047" means 64bit.

Oracle, stores data in segments. Segments has free and used space. The mark(a logical mark) between free and used space can be called as high water mark(HWM). When new data filled, the mark moves. On deleting records, oracle does not move back HWM. That is, you have unused data but, HWM sees as if it were filled data. When you shrink table such as alter table move command, this HWM refreshes itself.

When you delete from a table, a DML operation, oracle undos the changing. That is you can move back, with some additional works. But when you truncate a table, a DDL operation, oracle moves back the HWM. So this is faster than normal delete clause. With delete, you will fire existing triggers whereas truncate does not.

Truncate is especially is used instead of dropping and recreating tables. with truncate, no objects will become invalid and grants are remains the same

What Is Bottleneck ?

Bottleneck is the slowest operations of the set of operations. It is important to identify in the bottleneck in the system to know what needs to be turned to be better Performance and scalabilty.

Some Examples :-

The I/O system may become a bottleneck on large database system.

If a database used more memory than what’s available,paging and swapping will become a bottleneck.

In a RAC system the interconnect may be overloaded (cannot handle all data transfers

There is two method to connect sysdba user :-

with password

without password

sql> conn / as sysdba ------ without password

* Oracle database user must have sysdba privileges.
* Os user must add in dba group.
* In sqlnet.ora file must content "NTS" in below line

sqlnet.authentication_services = (NTS)
****************************************************
with password

sql>conn sys/pwd as sysdba ------- with password

prevent to connect without password.
* remove os user from dba group.
* edit sqlnet.ora file and change "none" to "nts" in below line.
sqlnet.authentication_services =(none)
Default value is nts when sqlnet.ora file created.
***************************** DBA ******************

cmd>imp file= log= full=y show=y indexfile=<> userid=system/password

for example

cmd>imp file=d:\test.dmp log=d:\tb\test.log full=y show=y indexfile=d:\tb\test.sql system/manager

after execute this commands,you should go to check indexfile and logfile.