About calculated variables

A calculated variable uses an expression to perform calculations with the values of other items or their properties to produce a value. AVEVA™ Production Management determines the value of the calculated variable at run time.

Comparison between stored variables and calculated variables

• Calculated variable items each have their own expression element. This stores and evaluates code script to determine the value of the calculated variable at run time.

• Stored variable items do not store an expression for evaluation, so do not evaluate themselves at run time. Stored variable items commit their samples to Server database, whereas calculated variable items commit their expression, not the resultant value.

  Stored variable	Calculated variable
  Does not store an expression	Stores an expression
  Does not evaluate value at run time	Determines value of the expression at run time
  Commits sample to server database	Commits expression to server database

Related topics

• Add and configure a calculated variable

• Calculated variable properties