Consider whether you need to include variables in your database after identifying the system operations you want to automate and the messages you want to match.
Predefined Variables
Determine the need to use predefined variables.
Can any of the information you need for pattern matching or action processing be recalled using predefined variables?
User-Defined Variables
Determine the need for user-defined variables.
Does information from a combination of messages create conditions that require an action?
Can information from one message be used to match another message?
Does the same message occur more than once over a period of time?
In all of these cases, you can use user-defined variables to store data from a message for later use.
Variables and Variable Groups
Determine the need for defining variables versus variable groups.
Do you need to retain a particular value, such as a count? If so, define a variable.
Does the information consist of multiple values, such as an error count for each device, or an unpredictable number of values, such as the status of multiple processes? If so, define a variable group.
Initial Values
Identify a reasonable initial value for a variable when the database is activated. Specify this value using the DEFAULT command in your variable definition.
Timeouts
Should a variable be reset to its default value after a specified period? If so, use the TIMEOUT command.
Retained Values
Does information from messages in an active database need to be recalled when another database is activated? If so, use the RETAINED option on the TYPE command.