Cloning and Refreshing an Oracle Database

Dear Friends and Blog Readers,

I have been asked many times about the Cloning and Refresh process of Oracle Database by emails of blog readers and the users of the Oracle Technology Network (OTN) Forums.

Even though the information about Cloning and Refreshing a Database process available over web widely or has already been discussed. Here, in this post, I would like to explain and provide the information on the following Questions about Cloning and Refreshing of a Database with my simple terms.

Terms used in this post:

Source System - the system to be cloned - Production
Target System - the newly created (or cloned) system – Non Production
Production Database – PROD
Test Database – TEST
Development Database - DEV

What is a Database Clone?

* A database clone is an activity/procedure which is performed by every DBA on regular basis or when there is a requirement or request to do so from the different departments i.e. Test/Development teams.

* Cloning is nothing but creating a copy of production system in to a test or development environment. i.e. Having an exact image of production database in test area.

* Cloning is a procedure for preparing and creating a test or development servers with the copy of Oracle production database for testing upgrades, migrating an existing system to new hardware.

* A cloning process includes a copy of Oracle Home (Directories and Binaries) backup and Database (Database related files) backup to prepare the instance on another server.

* Though, it is possible to clone a database on the same server, Oracle doesn’t suggest to clone a database on the same server, where the production database is running.

What is a Database Refresh?

* A Database Refresh is also referred to as a database clone. However, we don’t clone Oracle Home rather we clone the Database as refresh.

* Refreshing a database is something like applying the changes or updates of production database to the database where the database is already cloned. i.e. let’s say you have cloned a database a month back, and now you are asked for doing refresh of a database, then you will perform the backup of database and prepare the clone the instance again on test server. This is nothing but refreshing.

* Refreshing of a particular table, group of tables, schema, or tablespace will be done using traditional export/import, transportable Tablespaces, or data pump methods.

* When an Oracle patch is applied on Production System, or in doubt, you have to prepare and clone the database again with the copy of Oracle Home (Directories and Binaries) Backup and Database (Database related files) Backup to prepare the instance.

* The difference between Cloning and Refreshing is that cloning process includes Oracle Home and database Clone; where as Refreshing process only includes database clone.

* If seen, the words, Clone and Refresh are used interchangeably for the sake of convenient.

When and why we Clone a Database?

* Generally production (PROD) database is cloned for various reasons and needs i.e. for something to be tested or something to be developed later those to be moved to production.

* It’s normal and quite common thing is that whenever there is any change or update to be performed and do not know the impact or effect after applying it on production (PROD), it’s required to be applied and tested on *NON* production database first (TEST or DEV), after the confirmation of change success, given by the users, then the changes will be moved to production.

* A Cloned test instance (TEST) for testing team/environment is exclusively used for testing the changes or issues which will be come severe on Production. Oracle Support gives the solution as fix when there is an issue in the database, so this fix needs to perform or apply on test/development databases.

* A Cloned development instance (DEV) for development team/environment is used for developing the new changes and then deploying the same on Production.

* A Cloned patch instance is used for patching to know the impact and the time required to apply the same on Production.

How to clone an Oracle Database and different ways of cloning.

There are many possible methods available for cloning a database, but each of them has pros and cons, and significance. Following are the methods.

Using Cold (Offline) Backup:

This is an easy and simple method to perform a clone of a database. This method requires your production database (PROD) needs to be shutdown gracefully, and take the backup of the database related files i.e. Data files, Control files, Redo Log files, using Operating System commands i.e. cp or copy. This is not possible where your PROD database is running 24/7 and should be available continuously for users.

For syntax and the series of steps to perform the clone using cold backup, refer the following URLs from the reference.

References:
http://www.samoratech.com/TopicOfInterest/swCloneDB.htm
http://www.pgts.com.au/pgtsj/pgtsj0211b.html
http://www.jlcomp.demon.co.uk/faq/clone_db.html

Using Hot (Online) Backup:

In this method, backup of the database will be done online i.e. without shutting down the database.

For this, your Production Database is must be in Archive log mode. For syntax and the series of steps to perform the clone using hot backup, refer the following URLs from the reference.

Reference:
http://www.quest-pipelines.com/newsletter/cloning.htm
http://www.oralnx.com/index.php/2007/03/22/cloning-an-oracle-database/
http://www.shutdownabort.com/quickguides/clone_hot.php

Using RMAN Commands:

Cloning can also be performed using RMAN Backups and RMAN commands and it’s also an easy method to perform so. The RMAN DUPLICATE command is used to perform the clone. Until Oracle 9i, to clone the database, it is required to be the Source and Target systems should have the same OS i.e. it is not possible to clone across the platform. But as workaround, using export/import can be cloning the database across the platforms. But starting from Oracle 10g the RMAN capabilities have improved immensely. Cross platform cloning/duplicating a database can be done using RMAN CONVERT commands.

For syntax and the series of steps to perform the clone using RMAN Commands, refer the following URLs from the reference.

References:

Creating and Updating Duplicate Databases with RMAN

http://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/rcmdupdb.htm#i1008564

Cross-Platform Transportable Database: RMAN CONVERT DATABASE

http://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/dbxptrn002.htm#CHDCFFDI

Creating a Duplicate Database on a Local or Remote Host

http://sabdarsyed.blogspot.com/2007/06/clone-of-database-on-same-host-ie.html

http://download-east.oracle.com/docs/cd/B19306_01/backup.102/b14191/rcmdupdb005.htm

Pre & Post Cloning Steps/Changes:

* Do *NOT* set the clone database name as good as production database Name.

* It’s *NOT* mandatory to have the initialization parameter values of cloned instance similar to Production Instance.

* It is *NOT* mandatory to have the cloned instance in Archive log mode. Because unnecessarily archive log files are generated, which consume the hard disk space? If at all, the cloned instance crashed and need to be recovered, it can easily be again cloned from the production.

* After the clone, change the system users passwords i.e. SYS & SYSTEM, and for any critical users passwords.

* Disable the jobs which are not required to be run in the cloned instance.

* Change any application users tables from the cloned database which are still referring the Production Database i.e. Server IP, Port Details, Printer Details etc,

Other Useful Links:

OTN Forums on Cloning:
http://forums.oracle.com/forums/search.jspa?threadID=&q=clone+a+database&objID=f61&dateRange=all&userID=&numResults=30&rankBy=10001

Ask Tom Forums:

DB cloning -- what is it and why
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:575623107841

Creating test environment from production box
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:526422273445

Metalink Notes:

Note:245262.1 - Subject: Create a Duplicate Database with NOCATALOG on Same Node
Note:458450.1 - Subject: Steps to Manually Clone a Database
Note:388431.1 - Subject: Creating a Duplicate Database on a New Host.

Conclusion: These are only my views and outlines about cloning and need *NOT* to be the same with others or Oracle. One individual can still follow their cloning procedure documents which are there in place with them. I strongly suggest one to do the changes first in the test/development before doing it on Production. And also, use Oracle Documentations and Metalink Support for any kind of help.

Hope that this post helps you in understanding the Cloning and Refreshing activity of a database.

**Please leave your comments/suggestions about this post**.

Regards,
Sabdar Syed.
http://sabdarsyed.blogspot.com/

Clone of a database on the same Host i.e. Server (Linux RHEL -4)

Dear friends,

As we all know, Cloning of a Database can be done using different backup methods i.e. using cold backup/hot backup (ALTER TABLESPACE <tablespace_name> BEGING BACKUP), and RMAN Backup with DUPLICATE TARGET DATABASE.

Recently I have performed the cloning for one of our University databases using the RMAN backup and DUPLICATE TARGET DATABASE commands, on the same host i.e. same server.

Important Note: It is recommended NOT to clone the production database on the same server or host. But as a practice you can do it for any non-prod instances.

Below are the software details:

DB Name: PROD
DB Version: Oracle 10g Release 2 (10.2.0.1)
OS Version: Red Hat Enterprise Linux (RHEL) – 4

The steps which I have followed for cloning:

Perform the database backup using RMAN.

Login as ORACLE on Linux

$ su – oracle Password: xxxxxx (Issue the password here)

Check and set the ORACLE_HOME, ORACLE_SID, and other environment variables.

$ export ORACLE_HOME=/u01/app/oracle/product/10.2.0 $ export ORACLE_SID=prod $ echo $ORACLE_HOME

Note: Oracle user has a profile (.bash_profile) in which all required environment variables are set, whenever the oracle user logs in to the server the environment variables are set automatically.

Below are the .bash_profile contents.

$ vi. .bash_profile

# User specific environment and startup programs
PATH=$HOME/bin:/usr/bin:/usr/sbin:/usr/local/bin:$ORACLE_HOME/bin
export PATH
ORACLE_HOME=/u01/app/oracle/product/10.2.0
TNS_ADMIN=$ORACLE_HOME/network/admin
LD_LIBRARY_PATH=$ORACLE_HOME/lib:/usr/lib
ORACLE_SID=prod
export ORACLE_HOME
export TNS_ADMIN
export LD_LIBRARY_PATH
export ORACLE_SID

:q!

Check if the target database is in Archive log mode or not.

$ sqlplus / as sysdba

SQL> ARCHIVE LOG LIST;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 59
Next log sequence to archive 61
Current log sequence 61
SQL>

Here in our case the database is already configured for Archive log mode, and the archive log destination is used by Flash Recovery Area.

If your DB is in no Archive log mode then change the mode to Archive log.

Set FRA (Flash Recovery Area) in your init/spfile.ora

DB_RECOVERY_FILE_DEST=/u03/FRA
DB_RECOVERY_FILE_DEST_SIZE=4G

Startup up the database in mount state

$ sqlplus / as sysdba

SQL> STARTUP MOUNT;
SQL> ALTER DATABASE ARCHIVE LOG;
SQL> ALTER DATABASE OPEN;
SQL> ARCHIVE LOG LIST;

Connect to RMAN and target instance to perform RMAN backup

$ export ORACLE_SID=prod
$ rman target /

RMAN> BACKUP DATABASE PLUS ARCHIVELOG DELETE INPUT;

-: BACKUP DATABASE PLUS ARCHIVELOG:-

This command will take the backup of all database files and archived log files, and place them in flash recovery area (/u03/FRA/PROD/backupsets/__

/, all the backup files contain the extension with .bkp

To check and list the backup taken previously using RMAN’s LIST commands.

RMAN> LIST BACKUP;

Prepare the initialization parameter file (init.ora) for clone database.

Copy the target database init.ora file and rename it corresponding to you clone instance.

$ cd $ORACLE_HOME/dbs

Note: If you do not find the init.ora file for your target instance under the directory $ORACLE_HOME/dbs, may be you are using spfile or the init.ora file might have kept somewhere in another location;

If the spfile is being used, then create the pfile from spfile

SQL> CREATE PFILE FROM SPFILE;

$ cp –p initPROD.ora initTEST.ora

Edit the initialization parameter file (initTEST.ora) and update the following parameters accordingly to your clone instance.

USER_DUMP_DEST=
BACKGROUND_DUMP_DEST=
AUDIT_FILE_DEST=
CORE_DUMP_DEST=
USER_DUMP_DEST=
CONTROL_FILES=
DB_NAME=
INSTANCE_NAME=
SERVICE_NAMES=
DB_FILE_CONVERT_NAME=
LOG_FILE_CONVERT_NAME=

Note: In general, cloned instances are not kept in archive log mode, so you can remove or comment both parameters related to FRA, DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE

Create the password file for clone (TEST) instance.

$ export ORACLE_SID=test

$ cd $ORACLE_HOME/dbs

$ orapwd file=orapwtest password=sys

Note: Make sure that the Production (Target) password and Test (Clone) password for orapwd file must be same.

Prepare the listener and tnanemes.ora entries for clone (TEST) instance.

$ cd $ORACLE_HOME/network/admin

Open listener.ora file and add the TEST instance entry as below.

(SID_DESC =
(SID_NAME = test)
(ORACLE_HOME = /u01/app/oracle/product/10.2.0)
)

Open tnsnames.ora file and add the TEST instance entry as below.

test =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = unicorn.kware) (PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME =test)
)
)

Check the Prod and Test service can be pinged.

$ tnsping prod

$ tnsping test

Start the clone instance (TEST) in no mount state.

$ export ORACLE_SID=test
$ sqlplus / as sysdba

SQL> startup nomount;

SQL> select instance_name from v$instance;

INSTANCE_NAME
-------------------------
test

Connect to RMAN and target & auxiliary instances.

Open a new connection.

$ export ORACLE_SID=prod
$ rman target / auxiliary sys/sys@test

RMAN> RUN
2> {
3> ALLOCATE AUXILIARY CHANNEL AUX1 DEVICE TYPE DISK;
4> DUPLICATE TARGET DATABASE TO 'test';
5> }

Above command output will be a self explanatory, please go through the output generated.

RMAN> exit;

You are now done with clone process.

Checks to be performed after the clone process is finished

Execute the below steps in Test (Clone) instance, and cross check the result with the Production (Target) instance.

$ export ORACLE_SID=test

$ sqlplus / as sysdba

SQL> SELECT OPEN_MODE,NAME FROM V$DATABASE;

SQL> ARCHIVE LOG LIST;

SQL> SELECT NAME FROM V$TABLESPACE;

SQL> SELECT USERNAME FROM DBA_USERS;

SQL> SELECT COUNT(*) FROM DBA_OBJECTS WHERE STATUS='INVALID';


If you find invalid objects then you can compile them using $ORACLE_HOME/rdbms/admin/utlrp.sql

Reference:

http://download-east.oracle.com/docs/cd/B19306_01/backup.102/b14191/rcmdupdb005.htm

Conclusion:

I have followed the above procedure/steps as per our requirement in the University. I would request you to follow the complete method and other options from referenced link above.

With Best Regards,

Sabdar Syed,
Oracle DBA/ Apps DBA,
Oracle Certified Professional (OCP) 8i, 9i & 10g

My Blog: http://sabdarsyed.blogspot.com

Database Cloning Mistake !!!!!

Dear Friends,

The following errors were generated continuously in the test database alert log file.

1). ORA-25153: Temporary Tablespace is Empty

2). GATHER_STATS_JOB encountered errors. Check the trace file.

3). ORA-20000: Unable to analyze TABLE "SIRSI"."HEADING4", insufficient privileges or does not exist.

But when we query to see the information about temporary tablespace and tempfiles in the database, the following findings were observed.

## To check TEMP tablespace and tempfile details.

SQL> SELECT file_name, bytes FROM dba_temp_files;

no rows selected

SQL> SELECT * FROM v$tempfile;

no rows selected

SQL> SELECT * FROM v$tablespace WHERE name='TEMP';

TS# NAME INC BIG FLA ENC
---------- ------------------------------ --- --- --- ---
3 TEMP NO NO YES

SQL> SELECT tablespace_name, contents FROM dba_tablespaces WHERE tablespace_name='TEMP';

TABLESPACE_NAME CONTENTS
------------------------------ ---------
TEMP TEMPORARY

SQL> SELECT DISTINCT temporary_tablespace FROM dba_users;

TEMPORARY_TABLESPACE
------------------------------
TEMP

## Gather Schema Statistics.

In Oralce 10g, when the data of a table is grown to certain threshold value i.e. 10% of data, Automatically Gather Schema Statistics is performed on those tables.And also it needs enough free space in the temporary tablespace for sorting. Due to this reason above messages generated in the alert log file.

Cause: The TEST Database has recently been cloned from PRODuction Database. So, we realized that the step, adding a tempfile to the temp tablespace, was missed mistakenly. In fact the tempfile was copied and it is physically existing in the server, but not added to the TEMP tablespace as part of the cloning.

Solution:

ALTER TABLESPACE TEMP ADD TEMPFILE '/u01/app/oracle/product/10.2.0/oradata/test/temp01.dbf' REUSE;

After adding a tempfile to the TEMP tablespace, no errors generated regarding Gather Schema Statistics and temp tablespace afterward !!!.

Note: if you are receiving an error "ORA-20000: Unable to analyze TABLE "SIRSI"."HEADING4", insufficient privileges or does not exist." due to other reasons. Please take a look at the Oracle Metalink Note ID: 333966.1

This article, written by me, is also available in Oracle Metalink. Note ID: 427974.1

Best Regards,
Sabdar Syed.