This parameter is introduced in Oracle 8.1.
It is a HIDDEN parameter (ie: It begins with an UNDERSCORE).
It is documented here as this hidden parameter may need to be set when performing upgrade / downgrade type operations on a database.
This parameter can only be set in the init.ora file in Oracle8i.
It can be changed dynamically using ALTER SYSTEM in Oracle9i.
Description
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System triggers are a new feature in Oracle 8.1.
When _SYSTEM_TRIG_ENABLED is set to TRUE (the default) then system triggers are enabled.
In some cases it may be necessary to disable system triggers from firing by setting this parameter to FALSE.
This should only be done for short periods for specific operations.
It is not advisable to allow normal users onto the database whilst such triggers are disabled as system triggers may be used for audit or security checking by certain applications.