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Flow variables
Flow variables provide a means of passing information throughout a flow instance without requiring that the information to be passed through data links. flow variables are name-value pairs that persist, unless deleted.
Flow variables locations
Flow variables can be specified at different locations.
Design server UI settings
Some node types allow you to set flow variables using the Design Server UI settings dialog, in the Flow Designer canvas.

Flow variables
Flow variables provide a means of passing information throughout a flow instance without requiring that the information to be passed through data links. flow variables are name-value pairs that persist, unless deleted.
- Flow variables locations
  Flow variables can be specified at different locations.
  - Runtime REST API
    Flow Variables can be specified as query parameters of the Runtime REST API invocation of flows.
  - Mapping functions
    Flow variables can be defined and manipulated through flow library, flowlib functions.
  - Design server UI settings
    Some node types allow you to set flow variables using the Design Server UI settings dialog, in the Flow Designer canvas.
- Flow variables scope
  Under Flow Engine context, all flow variables (both custom and special) defined for the flow instance, go out of scope when the flow instance completes execution. It does not affect the flow variables of the other instance.
- Thread local flow variables
  A 'thread local flow variable' is a special variable, in that each thread running under a flow instance gets a copy of the flow variable when referenced. Each thread then works on its own copy during flow execution. Any action (get, set, delete, increment, decrement, resolve), on the thread local flow variable, is performed on the copy of the flow variable associated with that thread.

Design server UI settings

Some node types allow you to set flow variables using the Design Server UI settings dialog, in the Flow Designer canvas.

Specifying a flow variable is a must for certain node types, in order for them to function properly during flow execution.

For example: A router node in a flow definition requires that a flow variable be defined for routing the data to one or more outputs of the node, based on the criteria applied over the flow variable and its value.