Initialization parameters fall into various functional groups. For example, parameters perform the following functions:
Set limits for the entire database
Set user or process limits
Set limits on database resources
Affect performance (these are called variable parameters)
Variable parameters are of particular interest to database administrators, because these parameters are used primarily to improve database performance.
Database administrators can use initialization parameters to:
Optimize performance by adjusting memory structures, such as the number of database buffers in memory
Set database-wide defaults, such as the amount of space initially allocated for a context area when it is created
Set database limits, such as the maximum number of database users
Specify names of files or directories required by the database
Many initialization parameters can be fine-tuned to improve database performance. Other parameters should never be altered or should be altered only under the supervision of Oracle Support Services.
All initialization parameters are optional. Oracle has a default value for each parameter. This value may be operating system-dependent, depending on the parameter.