How Parameter Values Are Changed

The database administrator can adjust variable parameters to improve the performence of a database system Excatly which parameters most affect a system depends on numerous database characteristics and variables.

Some parameters can be changed dynamically by using the ALTER SESSION or ALTER SYSTEM statement while the instance is runnig. Unless you are using a server file, changes made using the ALTER SYSTEm statement are only in effect for the current instance. You must manually update the text intilization parameter file for the changes to be known the next time you start up an instance. When you use a server parameter file. you can update the parameters on disk. so that persist across database shutdown and startup.