Backtracking mechanism allows to record the execution state of the model, and roll back to a record state later in the execution.
An incremental checkpointing technique is used for backtracking. It requires to record only the state changes during the execution, but not the complete state (also known as snapshot) of the whole model. Actors to be backtracked must be transformed with the Ptolemy backtracking transformer. The models that uses these actors acquire the ability to record their states in checkpoints, and later to roll back to those checkpoints.