db_migratecatalog 
You migrate the database catalog.
The database catalog now uses the Unicode character set instead of the ASCII character set. This command does not affect the format of the user data in the database.
User passwords may have no more than 18 characters in ASCII databases and no more than 9 in Unicode databases. After the migration, all users can still use their existing passwords to log on, but only the first 9 characters are evaluated.
The duration of the migration depends on different factors, such as hardware, database size and so on. You can use the following information as an indication:
Duration of a catalog migration for the database of an R/3 system containing approx. 7,000 tables, on an Intel® Pentium® 3 computer with a 700 MHz processor: approx. 10 min.
Duration of a catalog migration for the database of an R/3 system containing approx. 33,000 tables and approx. 5,700 views, on an HP computer (no additional information): approx. 40 min.
Recommendation
In case an error occurs during migration, we recommend that you carry out a complete data backup in the ADMIN operational state before migrating the database catalog.
You also need to carry out another complete data backup after successful migration. This is the only way to ensure that you can restore the new version of your database instance in case of a database error later on. You can only switch the automatic log backup function on once you have executed a complete data backup.
Prerequisites
The database is in the OFFLINE operational state.
You have the server authorization AccessUtility.
Structure
db_migratecatalog
Result
The catalog data of the database instance has been converted into the Unicode format. The database is in the ONLINE operational state.