Tag: Database

Change Oracle Enterprise Manager 10g Password

Posted on by Osama Mustafa in Application
How to change the password of the Database User SYSMAN when the database is hosting a DB Control Repository. 

1.Stop the DB Control
On Unix
$ emctl stop dbconsole

On Windows
Open a Command Window and type
**> emctl stop dbconsole

2.Check that the DB Control is stopped
On Unix

$ emctl status dbconsole

On Windows
Open a DOS Command Window and type
**> emctl status dbconsole


3.Connect to the database as a user with DBA privilege with SQL*Plus and execute:

SQL> alter user sysman identified by ;

4.Check the new password 

SQL> connect sysman/[@database_alias]
 

5.Go to $ORACLE_HOME/host_sid/sysman/config do the following :

    1. Save the file emoms.properties to emoms.properties.orig
    2. Edit the file emoms.properties
      1. Search for the line beginning with:
        oracle.sysman.eml.mntr.emdRepPwd=
        Replace the encrypted value by the new password value
        Example:
        oracle.sysman.eml.mntr.emdRepPwd=rainbow
      2. Search for the line:
        oracle.sysman.eml.mntr.emdRepPwdEncrypted=TRUE
        Replace TRUE by FALSE

6.Restart the DB Control
On Unix

$ emctl start dbconsole
 
Open a DOS Command Window and type
**> emctl start dbconsole
 
 
7.Check that the password has been encrypted
  1. Edit the file $ORACLE_HOME/host_sid/sysman/config/emoms.properties
    1. Search for the line beginning with:
      oracle.sysman.eml.mntr.emdRepPwd=
      Check that the password is encrypted
    2. Search for the line beginning with:
      oracle.sysman.eml.mntr.emdRepPwdEncrypted=
      Check that the value is TRUE

I Publish the same lesson but on 11g .

  Thank you 
Osama mustafa  

 

Create Enterprise manager for RAC (Real Application Cluster)

Posted on by Osama Mustafa in Database
Hi All ,

Sometimes we need to create enterprise manager for Rac Environment , its the same way for One instance with different Command . 

We are here talk about 10g , 11g database .
you follow the below steps to create or recreate enterprise manager LET’S START :

if you already have RAC – enterprise manager and you need to recreate then start from here

**Stop Dbconsole for the both nodes :

Commands :

On Node-1
emctl stop dbconsole .
On Node 2 :
emctl stop dbconsole .

**Drop dbconsole with re posterity from node 1 :

Command :

$emca -deconfig dbcontrol db -repos drop -cluster

“you will wait for while until repos been dropped”.

**recreate dbconsole with re posterity from node 1 “if you don’t have EM for your Rac start from here”
Command :

$emca -config dbcontrol db -repos create -cluster 

“follow the instsruction and fill the information such as DB SID,Listener Port , Crs Name”

To know your CRS NAME :
$CRS_HOME/bin/cemutlo -n

the output will be your crs name .

Thank you
Osama mustafa 

Basic Rman (Recovery manager) Guide

Posted on by Osama Mustafa in Database
Today we are gonna talk about Oracle Rman ( Recovery Manager) This tools from oracle makes backup and restore database looks easily , If you lose you data it will be problem so oracle provide solution for this issue
Rman is Command line tools that gives you lot of benefits for backup
such as backup database, control file , archive log , create scripts … etc

you can connect to the following types of databases.

Target database : 
RMAN connects you to the target database with the SYSDBA privilege. If you do not have this privilege, then the connection fails.
Recovery catalog database: 
This database is optional, you can also use RMAN with the default NOCATALOG option.
Auxiliary database :
You can connect to a standby database, duplicate database, or auxiliary instance (standby instance or tablespace point-in-time recovery instance.

Connecting to the Target Database

rman target /

 Information About your Schema And display datafiles Currently In the target database .

RMAN>REPORT SCHEMA;

To list the backup sets and image copies that you have created, run the list command as follows:

 RMAN> LIST BACKUP;

To list image copies, run the following command:

RMAN> LIST COPY;

 Show Rman Confurgation :

RMAN>Show all ;

List All the backup has been taken by Rman :

RMAN>list backupset ;

Validate Your backup that has been taken  By Rman , to check there’s no corrputed file in it :
RMAN>validate backupset

Take anote that I mention Rman basic command in earlier Blog , Please take a look at it .
And ENJOY .

Thank you
Osama Mustafa

Usage of OS_AUTHENT_PREFIX

Posted on by Osama Mustafa in Database

1. Overview

1) OS_AUTHENT_PREFIX is an important initialization parameter to configure Oracle External User environment.
2) External User is a kind of Oracle External Authentication solution.
3) With Oracle External User, the user authentication process is accomplished by operating system automatically.
4) Authorized OS user can access Oracle database directly without providing username and password other than logon with prompting these information.

2. Official Reference

OS_AUTHENT_PREFIX
Parameter type
String
Syntax
OS_AUTHENT_PREFIX = authentication_prefix
Default value
OPS$
Modifiable
No
OS_AUTHENT_PREFIX specifies a prefix that Oracle uses to authenticate users attempting to connect to the server. Oracle concatenates the value of this parameter to the beginning of the user’s operating system account name and password. When a connection request is attempted, Oracle compares the prefixed username with Oracle usernames in the database.
The default value of this parameter is OPS$ for backward compatibility with previous versions. However, you might prefer to set the prefix value to “” (a null string), thereby eliminating the addition of any prefix to operating system account names
Note:
The text of the OS_AUTHENT_PREFIX parameter is case sensitive on some operating systems.
See Also:
l Your operating system-specific Oracle documentation for the default value
Create Oracle database user with OS authentication solution.

3.1 Prerequisite Checking

1) OS Environment
C:\Documents and Settings\ZYY> sqlplus “/as sysdba”
SQL*Plus: Release 10.2.0.1.0 – Production on 星期四 6月 11 17:02:49 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
连接到:
Oracle Database 10g Express Edition Release 10.2.0.1.0 – Production
SQL> SELECT OSUSER, USERNAME, PROGRAM FROM V$SESSION;
OSUSER USERNAME PROGRAM
——————– ——————– ——————–
SYSTEM ORACLE.EXE (q001)
SYSTEM ORACLE.EXE (QMNC)
SYSTEM ORACLE.EXE (q000)
YYBB\ZYY YYBB\ZYY sqlplus.exe
SYSTEM ORACLE.EXE (MMNL)
SYSTEM ORACLE.EXE (MMON)
SYSTEM ORACLE.EXE (CJQ0)
SYSTEM ORACLE.EXE (RECO)
SYSTEM ORACLE.EXE (SMON)
SYSTEM ORACLE.EXE (CKPT)
SYSTEM ORACLE.EXE (LGWR)
SYSTEM ORACLE.EXE (DBW0)
SYSTEM ORACLE.EXE (MMAN)
SYSTEM ORACLE.EXE (PSP0)
SYSTEM ORACLE.EXE (PMON)
Note:
n This practice is intended to be taken on Microsoft Windows platform.
n “YYBB” is the Computer Name on which runs the Windows OS.
n “ZYY” is the User Name which be used to logon to Windows OS.
2) Database Environment
SQL> SHOW PARAMETER OS_AUTHENT
NAME TYPE VALUE
———————————— ———————- ————–
os_authent_prefix string
remote_os_authent boolean FALSE
Note:
n The value of OS_AUTHENT_PREFIX parameter is set to “” (a null string).

3.2 Create External User

1) Create User in Oracle Database
SQL> CREATE USER “YYBB\ZYY” IDENTIFIED EXTERNALLY;
Note:
n In the above demo case, the value of OS_AUTHENT_PREFIX parameter is set to “” (a null string), the corresponding username in Oracle database should be YYBB\ZYY.
n If the value of OS_AUTHENT_PREFIX parameter is set to “OPS$”, the corresponding username in Oracle database should be OPS$YYBB\ZYY.
n Do NOT forget the Double Quotation Marks(“”) embrace the username YYBB\ZYY, otherwise, you will get an ORA-00911 warning against the special character \.
n Be aware of the keyword “EXTERNALLY”.
n Do NOT be reckless with “IDENTIFIED” which should NOT be followed by “BY”.
2) Grant Privileges to Oracle User
SQL> GRANT RESOURCE, CONNECT TO “YYBB\ZYY”;
Note:
n Grant appropriate and Minimum privileges to this Oracle user according to your system security acquirement.
n Oracle user name might be Case Sensitive on some platforms.

3.3 Test External User

1) Logon Oracle Database with External User
C:\Documents and Settings\ZYY>sqlplus /
SQL*Plus: Release 10.2.0.1.0 – Production on 星期四 6月 11 17:26:51 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
连接到:
Oracle Database 10g Express Edition Release 10.2.0.1.0 – Production
SQL>
Note:
n You do NOT need to provide username and password to logon to Oracle database through sqlplus.
2) Check the Current Logon User
SQL> SHOW USER
USER 为 “YYBB\ZYY“
SQL> SELECT USERNAME FROM DBA_USERS;
USERNAME
————————————————————
YYBB\ZYY
SYS
SYSTEM
MDSYS
OUTLN
XDB
Note:
n Current logon user is “YYBB\ZYY”.
n You can now access Oracle database via your OS user account directly.

Oracle Database Block corruption

Posted on by Osama Mustafa in Database

Oracle Database Block corruption

“Block corruption is rare but it does happen. As databases get larger and larger – the probability of it happening at some point nears 100%.”–Mr. Tom Kyte Oracle Expert

Block corruption is while the data is being written to the data blocks, if the write to the block fails abruptly, I mean that there is a partial write in the block, may be because of power disruption or I/O problem, leaving no time for header to be updated, or row data to be populated, oracle leaves the block corrupt.In case of block corruption you can normally use the database unless you try to read that particular block, against which it shoots up the block corruption error.Generally block corruption occurs if write fails on the block, when the transaction is being committed

ORA-01578:
ORACLE data block corrupted (file # string, block # string)
Whenever we encounter above error message mean we have BLOCK CORRUPTION.

NOTE: We can find detail information about block corruption in alert.log file

Two types of block corruption can happens

– Physical corruption (media corrupt)
– Logical corruption (soft corrupt)

Physical corruption can be caused by defected memory boards, controllers or broken sectors on a hard disk;

Logical corruption can among other reasons be caused by an attempt to recover through a NOLOGGING action.

Difference between logical and physical corruption

Logical corruption is header – footer – that is one of the checks, yes (it is looking for fractured blocks and when it hits one, it’ll re-read it, that is why there is no need for “alter tablespace begin backup” with rman)

Physical corruption is “we cannot read the block from disk, something is physically preventing us from doing so”.

How to detect block corruption?
1. DBVERIFY utility

DBVERIFY is an external command-line utility that performs a physical data structure integrity check. It can be used on offline or online databases, as well on backup files. You use DBVERIFY primarily when you need to ensure that a backup database (or datafile) is valid before it is restored.

http://dbataj.blogspot.com/2007/04/offline-database-verification-utility.html

2. Block checking parameters

There are two initialization parameters for dealing with block corruption:- DB_BOCK_CHECKSUM (calculates a checksum for each block before it is written to disk, every time)causes 1-2% performance overhead- DB_BLOCK_CHECKING (serverprocess checks block for internal consistency after every DML)causes 1-10% performance overhead

Note: In10g db_block_checksum value TYPICAL is implying TRUE and db_block_checking value FULL implying TRUE.

DB_BLOCK_CHECKING Initialization Parameter
http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/repair.htm#sthref3176

3. ANALYZE TABLE tablename VALIDATE STRUCTURE CASCADE SQL statement

Validate the structure of an index or index partition, table or table partition, index-organized table, cluster, or object reference (REF).

ANALYZE: Reporting Corruption
http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/repair.htm#sthref3173

4. RMAN BACKUP command with THE VALIDATE option

You can use the VALIDATE option of the BACKUP command to verify that database files exist and are in the correct locations, and have no physical or logical corruptions that would prevent RMAN from creating backups of them. When performing a BACKUP… VALIDATE, RMAN reads the files to be backed up in their entirety, as it would during a real backup. It does not, however, actually produce any backup sets or image copies.

Detection of Logical Block Corruption

Besides testing for media corruption, the database can also test data and index blocks for logical corruption, such as corruption of a row piece or index entry. If RMAN finds logical corruption, then it logs the block in the alert.log. If CHECK LOGICAL was used, the block is also logged in the server session trace file. By default, error checking for logical corruption is disabled.
For BACKUP commands the MAXCORRUPT parameter sets the total number of physical and logical corruptions permitted in a file. If the sum of physical and logical corruptions for a file is less than its MAXCORRUPT setting, the RMAN command completes successfully. If MAXCORRUPT is exceeded, the command terminates and RMAN does not read the rest of the file. V$DATABASE_BLOCK_CORRUPTION is populated with corrupt block ranges if the command succeeds. Otherwise, you must set MAXCORRUPT higher and re-run the backup to find out the corrupt block ranges.
RMAN found any block corruption in database then following Data Dictionary view populated.

V$COPY_CORRUPTION
V$BACKUP_CORRUPTION
V$DATABASE_BLOCK_CORRUPTION

Using RMAN to Validate Database Files
http://download.oracle.com/docs/cd/B19306_01/backup.102/b14192/bkup005.htm#i1006673

5. EXPORT/IMPORT command line utility

Full database EXPORT/IMPORT show=y is another method.

. about to export SCOTT’s tables via Conventional Path …
. . exporting table BONUS
EXP-00056: ORACLE error 1578 encountered
ORA-01578: ORACLE data block corrupted (file # 4, block # 43)
ORA-01110: data file 4: ‘C:\ORA10GHOME\ORADATA\ORCL10G\USERS01.DBF’

6. DBMS_REPAIR package

dbms_repair is a utility that can detect and repair block corruption within Oracle. It is provided by Oracle as part of the standard database installation.

http://www.oracleutilities.com/Packages/dbms_repair.html

How to Repair & Fix block corruption?

We can recover everything but we have valid database backup.
Whenever we found block corruption then first need to find out which type of block corruption occurred because block corruption recovery depends on block corruption type.

Like Corrupted block related to TABLE segment, INDEX segment, TABLE
PARTITION segment, INDEX PARTITION segment, ROLLBACK segment, LOB segment.

Through below query we can find out corrupted block type

select segment_type,owner’.’segment_name
from dba_extents
where file_id = [&file_id] and [&block] between block_id and block_id+blocks -1;

Below is example with RMAN BLOCK MEDIA RECOVERY.

SQL> conn scott/tiger
Connected.
SQL> select * from test;
select * from test
*
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 5, block # 11)
ORA-01110: data file 5: ‘C:\INDEXDATA01.DBF’

First check which type of block corruption happened through above mentioned query.

RMAN> blockrecover datafile 5 block 11;
Starting recover at 29-APR-08using channel
ORA_DISK_1 starting media recoverymedia recovery complete,
elapsed time: 00:00:00
Finished recover at 29-APR-08

If you are not using rman then applying below procedure
– if it is index then drop and recreate index
– if it is table and you have backup of that table then restore backup on another database and exp/imp the table.

How to corrupt database block for practice purpose?
On Unix:
Use dd command
$man dd

On Windows:
Use Editor and open datafile write some junk character at middle of file and save it.

i would thank taj for this amazing artical .