Database – how to change the maximum number of connection to Oracle database

In order to handle a database connection, a separate Oracle process is required, which may require up to 2 MB of memory. Normally an Oracle installation limits the number of concurrent connections based on the available memory and CPU configuration.

For example, let's say you have 50 customer accounts on the database with a maximum of 100 concurrent connections per account. If every account in average uses only 25% = 25 connections, the total average number would be 1250 connections. That means 2500 MB only for storing connection specific data. There is also processor time needed for context switching.

By setting limits on concurrent connections, you can ensure your transactions get through, and that some very active customer accounts don’t start to block your database server's resources. The number of connections is limited by the sessions parameter and your licensing. The sessions parameter controls the total number of connections including the Oracle background processes.

Adding more RAM to the server using a 64-bit Windows platform is a good idea, since you don’t have to spend a lot, even adding 16 GB of memory.

For detailed information of how configurations perform on realistic workload scenarios, read the Oracle E-Business Suite Standard Benchmark. Typically they have a large number of connections.

Your very first error is to modify an object owned by SYS. You should not UPDATE/DELETE/TRUNCATE any object owned by SYS unless expressly told by support. Oracle provides APIs (packages) and DDL commands (ALTER DATABASE, etc.) to interact with the system objects and you should not use anything else.

Now, this is not how you change the database character set. The very first hit on google "oracle change character set" provides an example of how to change your character set.

Since it is a fresh install I suggest you bite the bullet and reinstalls a clean database with the desired character set. If you really don't want to reinstall, I suggest you contact support.

Edit

Funnily, I browsed the MOS support site to find out how to change the character set and I found out this note Changing the Database Character Set [225912.1] with this interesting note:

There are still "dba's" out there who try to change the NLS_CHARACTERSET or NLS_NCHAR_CHARACTERSET by updating props$ . This is NOT supported and WILL corrupt your database. This is one of the best way's to destroy a complete dataset. Oracle Support will TRY to help you out of this but Oracle will NOT warrant that the data can be recoverd or recovered data is correct. You WILL be asked to do a FULL export and a complete rebuild of the database.

Please, do NOT update props$.