You can use user-defined variables or system variables in process instructions.

These are variables that you define yourself and use to transfer characteristic values from one process instruction to another. Depending on where you want to use a variable, you can specify whether it is a simple or global variable when you define it.

• Simple variable are user-defined variables whose values are only transferred within one PI sheet.
• Global variables are user-defined variables whose values can be exchanged as follows:

• Between different PI sheets of the same process order
• As data points using the internal interface Manufacturing Data Access

• Between PI sheets of different process orders
• Between PI sheets and cockpits
• Between different cockpits

These are variables whose values have been predefined by SAP.

You can now use the characteristic value that you have defined by way of the variable somewhere else in the control recipe. When you want to use variables, you must distinguish between simple and global variables.

• Simple variables
  To use simple variables, you need to specify the variable name.
• Global variables
  When you use global variables, you must distinguish between variables that you want to use in the ABAP list-based PI sheet or in the browser-based PI sheet.

• In ABAP list-based PI sheets (control recipe destination type 1), you only need to specify the variable name to use global variables.

• In browser-based PI sheets (control recipe destination type 4), you have the following options:

• If you want to exchange variables between PI sheets and cockpits, you must use the internal interface Manufacturing Data Access.
• If you want to exchange variables between PI sheets of the same process order, you can use the declaration method.