Sunday, 11 November 2012

DATABASE MIGRATION FROM WINDOWS TO LINUX USING RMAN

Database Migration From Windows to Linux Using RMAN

This article describes the procedure to migrate a database from Windows to Linux using the "RMAN Convert Database" command.

In my environment , both Windows and Linux platforms have the same endian format, which makes possible to transfer the whole database, making the migration process very straightforward and simple.


To migrate between platforms that have a different endian format, Cross Platform Transportable Tablespaces needs to be used instead, which would not be discussed in this article.


Endian Format is a term that describe the order, in which, sequence of bytes are stored in computer memory. There are 2 endian format named "Little Endian" and "Big Endian". Linux, Windows use "Little Endian" byte order whereas Solaris, HPUX, Apple Mac use "Big Endian" byte order.


In Oracle 10g and onwards , following SQL should tell you which operating systems follow which byte order:


select * from v$transportable_platform order by platform_id;


The Windows Database:

SQL> select * from v$version;


BANNER

----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi
PL/SQL Release 10.2.0.4.0 - Production
CORE 10.2.0.4.0 Production
TNS for 64-bit Windows: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

SQL> select name from v$datafile;


NAME

----------------------------------------------------
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\SYSTEM01.DBF
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\UNDOTBS01.DB F
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\SYSAUX01.DBF
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\USERS01.DBF
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\EXAMPLE01.DB F

SQL> select name from v$controlfile;


NAME

----------------------------------------------------
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\CONTROL01.CT L
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\CONTROL02.CT L
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\CONTROL03.CT L


SQL> select member from v$logfile;


MEMBER

------------------------------------------------
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\REDO03.LOG
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\REDO02.LOG
C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\REDO01.LOG



List of Steps Needed to Complete the Migration:


The migration process is simple, but as it has several steps it is convenient to be familiar with them before running it:


1. Check platform compatibility between source and target OS

2. Start the database in read only mode
3. Check database readiness for transport from Windows to Linux using DBMS_TDB.CHECK_DB
4. Check if there are any external objects
5. Execute the RMAN Convert database command
6. Copy converted datafiles, generated Transport Script and Parameter File to Linux
7. Edit the init.ora for the new database
8. Edit the Transport Script and Parameter File changing the windows paths to Linux Paths
9. Execute the Transport Script
10. Change the Database ID
11. Check database integrity

1. Check platform compatibility between source and target OS:


First we need to check the platforms to be sure they have the same endian format, also we need to save the

PLATFORM_NAME string to use it later as part of the convert database syntax in RMAN.

SQL> select * from v$transportable_platform where PLATFORM_NAME='Microsoft Windows IA (64-bit)' or PLATFORM_NAME like 'Linux%' order by platform_id;


PLATFORM_ID PLATFORM_NAME ENDIAN_FOR

----------- ---------------------------------------- ----------
8 Microsoft Windows IA (64-bit) Little
10 Linux IA (32-bit) Little
11 Linux IA (64-bit) Little
13 Linux x86 64-bit Little


2. Start the database in read only mode:


SQL> shutdown immediate;

SQL> startup mount;
SQL> alter database open read only;


3. Check database readiness for transport from Windows to Linux:


Before converting the database, we have to be make sure that whether a database can be transported to a desired destination platform, and whether the current state of the database permits transport. We check this using "DBMS_TDB.CHECK_DB" procedure.


If this procedure returns "FALSE" then the output includes the reason why the database cannot be transported like target platform has a different endian format, database is not open read-only, there are active transactions in the database, database compatibility version is below 10 etc.


SQL> set serveroutput on

SQL> declare
2 db_ready boolean;
3 begin
4 db_ready := dbms_tdb.check_db('Linux IA (64-bit)');
5 end;
6 /
PL/SQL procedure successfully completed.

If database is not open in read-only mode, then the above procedure may return error like "Database is not open READ ONLY. Please open database READ ONLY and retry."



4. Check if there are any external objects:


If there is any external objects take note of them, they will need to be taken care manually because RMAN cannot automate the transport of such objects. "DBMS_TDB.CHECK_EXTERNAL" must be used to identify any external tables, directories or BFILEs.


SQL> set serveroutput on

SQL> declare
2 external boolean;
3 begin
4 external := dbms_tdb.check_external;
5 end;
6 /
The following external tables exist in the database:
SH.SALES_TRANSACTIONS_EXT
The following directories exist in the database:
SYS.DATA_PUMP_DIR, SYS.ORACLE_OCM_CONFIG_DIR, SYS.ADMIN_DIR, SYS.WORK_DIR,
SYS.DATA_FILE_DIR, SYS.LOG_FILE_DIR, SYS.MEDIA_DIR, SYS.XMLDIR, SYS.SUBDIR
The following BFILEs exist in the database:
PM.PRINT_MEDIA

PL/SQL procedure successfully completed.



5. Using the RMAN CONVERT DATABASE Command:


After all the pre-requisites have been performed successfully, we can use the RMAN CONVERT DATABASE command to generate the output files for the target database.


While executing the CONVERT DATABASE command, we need to specify the new database name, the destination platform, path to save the transport script and optionally a path, where to save the output files using "DB_FILE_NAME_CONVERT". If you omit the "DB_FILE_NAME_CONVERT" clause, the output files are created in "$ORACLE_HOME\database" folder.


If you are using Oracle Managed Files(OMF), then RMAN itself generate and display the new file names on the output of the convert database command.




C:\Users\dell>rman target /


RMAN> CONVERT DATABASE NEW DATABASE 'orcllnx'

2> transport script 'C:\oracle\trans\script.sql'
3> to platform 'Linux IA (64-bit)'
4> db_file_name_convert 'C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\' 'C:\ORACLE\TRANS\';

Starting convert at 09-JAN-12

using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=158 devtype=DISK
.
.
.
User SYS with SYSDBA and SYSOPER privilege found in password file
channel ORA_DISK_1: starting datafile conversion
input datafile fno=00001 name=C:\ORACLE\PRODUCT\10.2.0\ORADATA\ORCL\SYSTEM0 1.DBF
converted datafile=C:\ORACLE\TRANS\SYSTEM01.DBF
channel ORA_DISK_1: datafile conversion complete, elapsed time: 00:00:25
.
.
.
Run SQL script C:\ORACLE\TRANS\SCRIPT.SQL on the target platform to create database
Edit init.ora file C:\ORACLE\PRODUCT\10.2.0\DB_1\DATABASE\INIT_00N0BG 62_1_0.ORA. This PFILE will be used to create the database on the target platform
To recompile all PL/SQL modules, run utlirp.sql and utlrp.sql on the target platform
To change the internal database identifier, use DBNEWID Utility
Finished backup at 09-JAN-12

Note that at the end of the convert process RMAN does display information about how to complete the conversion on the target platform.


You can use the init.ora file generated by the "CONVERT DATABASE" command or you can create your own pfile using the SQL statement "create pfile from spfile". I am going with the init.ora, generated by RMAN.



6. Copy Converted Datafiles, Generated Transport Script and Parameter File to the Linux:


Now copy these converted datafiles, transport script and parameter file on the Linux server using FTP or any other utility you use.


Also create the necessary folders on Linux server for new database.


[oracle]$ mkdir -p /u01/app/oracle/admin/orcllnx/adump

[oracle]$ mkdir -p /u01/app/oracle/admin/orcllnx/bdump
[oracle]$ mkdir -p /u01/app/oracle/admin/orcllnx/cdump
[oracle]$ mkdir -p /u01/app/oracle/admin/orcllnx/udump
[oracle]$ mkdir -p /u01/app/oracle/oradata/orcllnx
[oracle]$ mkdir -p /u01/app/oracle/flash_recovery_area


7. Edit init.ora for new database:


Open the init.ora file generated by RMAN using a editor you preferred. You will notice that the init.ora file is divided into 3 sections as denoted by the following comment:


# Please change the values of the following parameters:

# Please review the values of the following parameters:
# The values of the following parameters are from source database:

The first section must be updated, others are optional. Change all the absolute path of windows environment to absolute path of Linux environment.

8. Edit The Transport Script:


Before running the transport script on the target Linux server we need to edit it to set the correct paths for pfile, datafiles, logfiles and tempfiles. Update all the paths as per your Linux environment.


9. Execute the Transport Script:


[oracle]$ export ORACLE_SID=orcllnx

[oracle]$ sqlplus / as sysdba
SQL> @script.sql

On the completion of the script, the database would be open and ready for use.


10. Change database identifier:


DBNEWID is a database utility that can change the internal database identifier (DBID). It is run when the database is mounted.


[oracle]$ sqlplus / as sysdba

SQL> startup mount;
SQL> exit

[oracle]$ nid TARGET=/ # ORACLE_SID must be set


After completing the above command, open the database with RESETLOGS option.


[oracle]$ sqlplus / as sysdba

SQL> startup mount;
SQL> alter database open resetlogs;


11. Check database integrity:


SQL> select tablespace_name from dba_tablespaces;

SQL> select file_name from dba_data_files;

Checking component status after transport:


SQL> SELECT COMP_NAME,STATUS FROM DBA_REGISTRY;

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