HOW TO
When migrating an Oracle database from one platform to another, there are several factors to take into consideration.
The first of these is called endianness format.
Endianness format refers to the byte order of the data on disk, and is dependent on the CPU and operating system.
It is not possible to simply move Oracle database datafiles between systems with different endianness formats.
Endianness format refers to the byte order of the data on disk, and is dependent on the CPU and operating system.
The migration for each of these methods will start with step where :-
The creation of a new database on the new platform.
This is due to the fact that with each of these methods, the SYSTEM and SYSAUX tablespaces cannot be migrated across platforms.
After this initial step, the details of migration for each method do differ.
The available migration methods are:
* Export and Import
* Cross Platform Transportable Tablespaces (XPTTS) - This method allows datafiles to be moved between platforms of different endian format. Recommended for performing platform migration to a different endian format.
* Cross-platform transportable database - This method is suitable where source and target platform must be the same indian format.
Migration Method
You can use the Data Pump export and import utilities to migrate an Oracle database between platforms and OS environments, but it can be very slow for large systems.
When using this method, the data from the source database is exported to a flat file. The flat file is copied to the destination system, and then the data is imported into the destination database.
Benefit
* It is the simplest method of migration and utilizes tools that all DBAs should be familiar with.
* There are very few restrictions on the data and data types that can be migrated.
* There is very little setup needed prior to the migration.
Disadvantage
* For large databases the migration process can take a long time.
* The process is fairly dull and there are no new tools to play with.
In this method, we can plug datafiles into a database on a different platform, including those that are using a different endian format.
It reduces platform migration time by moving all user tablespaces from a source database to an empty target database running on a platform that uses a different endian format.
With the XTTS feature, tablespace datafiles are plugged into the empty target database by copying the datafiles to the target database, converting them to the target system endian format, and then importing the object metadata into the target database.
This set can be just one tablespace, or up to all of the tablespaces in the database, except for system, undo, and temporary tablespaces.
Steps
Make tablespaces in source database READ ONLY
Transfer data files to destination system
Convert datafiles to destination system endian format
Export metadata of objects in the tablespaces from source database using Data Pump
Import metadata of objects in the tablespaces into destination database using Data Pump
Make tablespaces in destination database READ WRITE
Benefit
* There are a lot of steps, this migration method is still fairly straightforward.
* There are very few database and data type restrictions.
* For larger databases, this method is usually much faster than the export and import methods.
Disadvantage
* There are a lot of steps in this process that need to be performed in the proper order.
* For databases that have a large amount of metadata, the export and import of the metadata can take a very long time.
* Some applications such as Oracle E-Business Suite have a large amount of metadata.
* This method may still require a significant amount of down time.
* There can be a significant amount of setup time.
A cross-platform transportable database is that the source and destination platform must share the same endian format.
Restraction
* The source and destination platform must share the same endian format.
* Redo log files and control files from the source database are not transported.
* New control files and redo log files are created for the new database during the transport process, and an Open Resetlogs is performed once the new database is created.
* Similarly, temp files belonging to locally managed temporary tablespaces are not transported.
* The temporary tablespace will be re-created on the target platform when the transport script is run.
* BFiles, External tables and directories, Password files are not transported.
* The Source and the target database version must be equal / greater than 10.2.0. Version
* If your goal is to migrate a database to different endian platform, then you need to perform below steps :
* Create a new, empty database on the destination platform.
* Import objects required for transport operations from the source database into the destination database.
* Export transportable metadata for all user tablespaces from the source database.
* Transfer data files for user tablespaces to the destination system.
* Use RMAN to convert the data files to the endian format of the destination system.
* Import transportable metadata for all user tablespaces into the destination database.
* You could also convert the datafiles at the source platform and once converted transfer them to the destination platform.
