I want to migrate my Oracle database from 7.3 to 8i. Which one is better: migration utility or export/import and why?
Which method is better depends on a number of factors. I will expand on this some more, but first, I suggest that you read a copy of the Oracle 8i Migration Guide thoroughly. It covers this topic in great detail. You can get a copy on Technet.
The export/import method has three big advantages. By exporting the data, recreating the database as the new version, and importing the data, you can reduce chained/migrated rows. You can reduce object fragmentation by coalescing objects into one extent. And since you are recreating the database as the new version, you get a chance to change the DB_BLOCK_SIZE, or other database configurations. The disadvantage of this method is that it takes the longest time to implement. The amount of time to import the data is directly influenced by the amount of data in your database.
The migration utility is the quickest method. And the amount of data in your database does not have an influence on your migration time. But you cannot change your DB_BLOCK_SIZE during the migration, or take advantage of the other stuff outlined above with the export/import method.
I've used both methods to perform my migrations. If time is not a crucial issue, then you may consider the export/import method. If your database is a 24x7 system, then downtime is an issue, and the migration utility is probably your best method. No matter which method you choose, make sure you take a backup both before and after your migration!
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This was first published in June 2001