Data Guard Background processes

DMON – The Data Guard Broker process.

SNP – The snapshot process.

MRP – Managed recovery process – For Data Guard, the background process that applies archived redo log to the standby database.

ORBn – performs the actual rebalance data extent movements in an Automatic Storage Management instance. There can be many of these at a time, called ORB0, ORB1, and so forth.

OSMB – is present in a database instance using an Automatic Storage Management disk group. It communicates with the Automatic Storage Management instance.

RFS – Remote File Server process – In Data Guard, the remote file server process on the standby database receives archived redo logs from the primary database.

QMN – Queue Monitor Process (QMNn) – Used to manage Oracle Streams Advanced Queuing.

How to set Data Protection Mode of a Primary Database

Step 1 Select a data protection mode that meets your availability, performance and data protection requirements.

Step 2 Verify that redo transport is configured to at least one standby database The value of the LOG_ARCHIVE_DEST_n database initialization parameter that corresponds to the standby database must include the redo transport attributes listed for the data protection mode that you are moving to.

Maximum Protection, Availability – AFFIRM,SYNC, DB_UNIQUE_NAME
Maximum Performance – NOAFFIRM, ASYNC, DB_UNIQUE_NAME

Step 3 Verify that the DB_UNIQUE_NAME database initialization parameter has been set to a unique name on the primary and standby database.

Step 4 Verify that the LOG_ARCHIVE_CONFIG database initialization parameter has been defined on the primary and standby database and that its value includes a DG_CONFIG list that includes the DB_UNIQUE_NAME of the primary and standby database.

SQL> ALTER SYSTEM SET LOG_ARCHIVE_CONFIG=’DG_CONFIG=(MMPRY,MMSTB)’;

Step 5 Shut down the primary database and restart it in mounted mode if the protection mode is being set to Maximum Protection or being changed from Maximum Performance to Maximum Availability. If the primary database is an Oracle Real Applications Cluster, shut down all of the instances and then start and mount a single instance.
For example:
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;

Step 6 Set the data protection mode.
Execute the following SQL statement on the primary database:
SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE {AVAILABILITY | PERFORMANCE | PROTECTION};

Step 7 Open the primary database.
SQL> ALTER DATABASE OPEN;

Step 8 Confirm that the primary database is operating in the new protection mode.

SQL> SELECT PROTECTION_MODE FROM V$DATABASE;

When you create a Logical standby it is not required it should be same version of Primary database and OS also can be different. But in general Database version and OS should be same.

How does it work?
In a nutshell redolog data is shipped from the source data to the target database through Oracle Net services.

SOURCE
log_archive_dest_1=’localpath/’
INSTANCE NAME:MHGTST

TARGET
log_archive_dest_1=’localpath/’
INSTANCE NAME:STDTST

Creating a Physical Standby
1. Verify that the database is in force logging mode.

SQL>SELECT FORCE_LOGGING FROM v$database;

_________
NO

2. If it is not in force logging mode set the database in force logging mode.

SQL>ALTER DATABASE FORCE_LOGGING;

Also ensure that the database in archivelog mode, no archive log mode no STANDBY

3. Check whether log_archive_dest_2 is already set.
If it is set then use log_archive_dest_3

SQL> ALTER SYSTEM SET log_archive_dest_3=’SERVICE=stdtst’;

System altered.

4. Shutdown the source database

SQL> shutdown immediate;

Database closed.
Database dismounted.
ORACLE instance shut down.

5. cp the datafiles to the new location

cd /home/oracle/oracle/oradata/mhgtst /home/oracle/oracle/oradata/stdtst
copy the admin tree ( bdump, cdump, pfile etc. ) to the new location
cp -rp /home/oracle/oracle/product/10.2.0/db_1/admin/mhgtst \
/home/oracle/oracle/product/10.2.0/db_1/admin/stdtst

6.
SQL> startup mount;

ORACLE instance started.

7. create the standby control file

SQL> alter database create standby controlfile as ‘/tmp/stdtst.ctl’;

Database altered.

8. open the source db for other users
SQL> alter database open;

Database altered.

9.CREATE the pfile from spfile and make changes so that all references to mhgtst now point to stdtst.
db_unique_name should still be the same in both the databases.

Make the following changes to the init.ora file of the STANDBY
dataabase:-
*.user_dump_dest=’/home/oracle/oracle/product/10.2.0/db_1/admin/stdtst/udump’
*.db_file_name_convert=’mhgtst’,'stdtst’
*.log_file_name_convert=’mhgtst’,'stdtst’;
*.db_name=’stdtst’;
*.db_unique_name=stdtst

10. Create password file for the standby database.
orapwd file=stdtst entries=2 password=oracle

11. Make final changes
Remove the log_archive_dest_3 from the standby init.ora file.
Create the appropriate entires for log_archive_dest_1 and
log_archive_dest_2

mkdir -p /home/oracle/oracle/logarch/stdtst/dest_1
mkdir -p /home/oracle/oracle/logarch/stdtst/dest_2

12. Mount the database

export ORACLE_SID=stdtst
SQL>startup nomount;

Oracle Instance started

13. Try to mount the database:-
copy the control file from the source database

[oracle@racdb1 stdtst]$ cp /tmp/stdtst.ctl ./control01.ctl
[oracle@racdb1 stdtst]$ cp /tmp/stdtst.ctl ./control02.ctl
[oracle@racdb1 stdtst]$ cp /tmp/stdtst.ctl ./control03.ctl

SQL> alter database mount standby database;

alter database mount standby database
*
ERROR at line 1:
ORA-01103: database name ‘MHGTST’ in control file is not ‘;’

In previous versions of oracle database we had to set LOCK_NAME_SPACE parameter, this is a obsolete / deprecated parameter in 10g.

VERY IMPORTANT

Your db_name in the standby instance should be pointing to the source db name.
db_name=mhgtst
This is the source db name.

SQL> alter database mount standby database
2 /

Database altered.

14. Recover the stand by database
SQL> recover standby database;
ORA-00279: change 1174794 generated at 08/04/2006 08:48:11 needed for thread 1
ORA-00289: suggestion :
/home/oracle/oracle/logarch/stdtst/dest_2/1_8_597228601.dbf
ORA-00280: change 1174794 for thread 1 is in sequence #8

Specify log: {suggested | filename | AUTO | CANCEL}

If you want the process to do recovery in background issue the command below:-

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

15. Validation
Switch the logfile on the source so that the log file is applied to the target database.
mhgtst -> stdtst

The alert.log should have the following entries in it:-
Media Recovery Log /home/oracle/oracle/logarch/stdtst/dest_1/1_51_597228601.dbf
Media Recovery Log
/home/oracle/oracle/logarch/stdtst/dest_1/1_52_597228601.dbf
Media Recovery Waiting for thread 1 sequence 53 Fri Aug 4 12:33:53 2006
RFS[1]: No standby redo logfiles created
RFS[1]: Archived Log:
‘/home/oracle/oracle/logarch/stdtst/dest_1/1_53_597228601.dbf’
Fri Aug 4 12:33:58 2006
Media Recovery Log
/home/oracle/oracle/logarch/stdtst/dest_1/1_53_597228601.dbf
Media Recovery Waiting for thread 1 sequence 54 Fri Aug 4 12:34:50 2006
RFS[1]: No standby redo logfiles created
RFS[1]: Archived Log:
‘/home/oracle/oracle/logarch/stdtst/dest_1/1_54_597228601.dbf’
Fri Aug 4 12:34:53 2006

16. Canceling recover managed database

SQL>ALTER DATABASE STANDBY DATABASE CANCEL;

Database Altered

17.ALTER DATABASE OPEN;

DB is now open for normal operations

18. Use queries till the application is up and running. In the mean time remember
there are a few log switches in the source database.
TARGET
SHUTDOWN IMMEDIATE and put the physical database in recover mode.

STARTUP MOUNT;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION
/

ERRORS
ORA-01678: parameter log_file_name_convert must be pairs of pattern and replacement strings
There was a semicolon at the end of the log_file_name_convert, remnove that and the
database was able to start in nomount mode.
Please check your setting for log file name convert parameter.

Media Recovery Start
Managed Standby Recovery not using Real Time Apply
ORA-279 signalled during: ALTER DATABASE RECOVER standby database …

SQL> alter database recover managed standby database disconnect from
SQL> session;

ORA-12154: TNS:could not resolve the connect identifier specified
PING[ARC0]: Heartbeat failed to connect to standby ‘stdtst’. Error is 12154.

This error is because we have not yet configured the name stdtst service.

Configure the listener
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = mhgtst)
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = stdtst)
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
(PROGRAM = extproc)
)
)

Reload the listener
Listening Endpoints Summary…
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=1521)))
Services Summary…
Service “PLSExtProc” has 1 instance(s).
Instance “PLSExtProc”, status UNKNOWN, has 1 handler(s) for this service…
Service “mhgtst” has 1 instance(s).
Instance “mhgtst”, status UNKNOWN, has 1 handler(s) for this service…
Service “stdtst” has 1 instance(s).
Instance “stdtst”, status UNKNOWN, has 1 handler(s) for this service…

Configure tnsnames
STDTST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = STDTST)
)
)

Verify tnsping
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = STDTST))) OK (20 msec)

Switch the log file and see if it is been sent to the service.

ORA-28547: connection to server failed, probable Oracle Net admin error
PING[ARC0]: Heartbeat failed to connect to standby ‘stdtst’. Error is 28547.

Usually this error means that there is some incompatibility in sqlnet.ora , tnsnames.ora and listener.ora SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = mhgtst )
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
)
(SID_DESC =
(SID_NAME = stdtst )
(ORACLE_HOME = /home/oracle/oracle/product/10.2.0/db_1)
)
)

SQL> alter database mount standby database;
alter database mount standby database
*
ERROR at line 1:
ORA-00205: error in identifying control file, check alert log for more info This error is because we didn’t put the control file from the source whe we issued a standby control file command.

DataGuard SWITCH OVER
Phase 1 PRIMARY:
1) SELECT SWITCHOVER_STATUS FROM V$DATABASE;
2) /**** ALTER SYSTEM SET remote_archive_enable=RECEIVE SCOPE=SPFILE;/
ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY WITH SESSION SHUTDOWN; (If you get SESSIONS_ACTIVE in 1, otherwise not needed)
3) ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY;
4) SHUTDOWN IMMEDIATE;
5) STARTUP NOMOUNT;
6) ALTER DATABASE MOUNT STANDBY DATABASE;
7) ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE;

Phase 2 STANDBY:
1) SELECT SWITCHOVER_STATUS FROM V$DATABASE;
2) /****ALTER SYSTEM SET remote_archive_enable=SEND SCOPE=SPFILE;/
3) ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
4) SHUTDOWN IMMEDIATE;
5) STARTUP;

— Switch from Standby to Primary 9i & 10g
1. Apply upto the last log

SQL> startup nomount

SQL> alter database mount standby database;

Database altered.

SQL> select PROTECTION_MODE from v$database;

PROTECTION_MODE
——————–
MAXIMUM PERFORMANCE

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH SKIP STANDBY LOGFILE;
( without stand-by redologs )
or

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH;
( with stand-by redologs )
Database altered.

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

Database altered.

SQL> select * from v$instance;
SQL>
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup
Database mounted.
Database opened.
SQL>

Maximum Performance
Updates committed to primary and sent to standby without waiting to see if they were applied to standby
Pros: Little or no effect on performance of primary
Cons: Slight chance of lost transactions (on failover)
Maximum Availability
Attempts to apply updates to standby before committed to primary
Lowers protection to Maximum Performance temporarily if updates can’t be applied to standby
Pros: Primary continues unaffected if connection to standby is lost or the updates are delayed
Cons: Slight performance hit on primary; lost transactions on failover possible only if the standby has been unreachable
Maximum Protection
Assures updates are applied to standby before committed to primary
Pros: No chance of lost transactions
Cons: Primary will freeze if connection to standby is lost or the updates are delayed