About Changing Initialization Parameter Values

The ALTER SYSTEM statement enables you to set, change, or restore to default the values of initialization parameters. If you are using a text initialization parameter file, the ALTER SYSTEM statement changes the value of a parameter only for the current instance, because there is no mechanism for automatically updating text initialization parameters on disk. You must update them manually to be passed to a future instance. Using a server parameter file overcomes this limitation.

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There are two kinds of initialization parameters:

• Dynamic initialization parameters can be changed for the current Oracle Database instance. The changes take effect immediately.
• Static initialization parameters cannot be changed for the current instance. You must change these parameters in the text initialization file or server parameter file and then restart the database before changes take effect.
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 Setting or Changing Initialization Parameter Values

With a server parameter file, use the SET clause of the ALTER SYSTEM statement to set or change initialization parameter values.

• Run an ALTER SYSTEM SET statement.

For example, the following statement changes the maximum number of failed login attempts before the connection is dropped. It includes a comment, and explicitly states that the change is to be made only in the server parameter file.

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The next example sets a complex initialization parameter that takes a list of attributes. Specifically, the parameter value being set is the LOG_ARCHIVE_DEST_n initialization parameter. This statement could change an existing setting for this parameter or create a new archive destination.

When a value consists of a list of parameters, you cannot edit individual attributes by the position or ordinal number. You must specify the complete list of values each time the parameter is updated, and the new list completely replaces the old list.

• The SCOPE Clause in ALTER SYSTEM SET Statements
  The optional SCOPE clause in ALTER SYSTEM SET statements specifies the scope of an initialization parameter change.

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