Usage of Database, schemas and tablespace

Question

we are working on data migration of sql server 2000 to Oracle 11g. Sql server has 4 databases which has to be migrated. These 4 databases are used for 6 different standalone applications. Oracle is installed in Unix server. Can we create a single database and different schemas for each sql server database or do I need to create multiple databases or can I use single database, single schema and multiple tablespaces or any other procedure to maintain the performance?

Answer 1

You can create multiple Oracle databases. Or you can create a single database with multiple schemas. Or you can create a single database with a single schema an put everything there if all your object names are unique.

The most similar approach would generally be to create a single Oracle database with four schemas. That gives you four separate namespaces in case you have objects in two different SQL Server databases that have the same name. And a single Oracle database per server generally gives the best performance since you're not allocating multiple SGAs and PGAs in memory or running multiple sets of background processes.

Tablespaces in Oracle are a completely separate concept. They have nothing to do with namespaces or permissions. They simply allow you to determine which objects reside in which physical data files. Barring something extremely unusual, tablespaces have nothing to do with performance. You could have the objects in all four schemas use a single tablespace. Or you could create four separate tablespaces. Or you could create multiple tablespaces that each have objects from different schemas. My guess is that the simplest approach is to create one tablespace per schema so that you can manage each application's disk space allocation separately.