Checkpoints define points in a program, at which the state of the program can be tested during program execution. Checkpoints are either conditional und unconditional. Conditional checkpoints are defined by assertions (as of release 6.20), unconditional checkpoints by break points or log points (as of release 7.0) You can activate and deactivate assertions as well as break points from outside of the program by assigning them to a checkpoint group (also as of release 6.20) via the transaction SAAB.
More information about activatable checkpoints in the documentation activatable checkpoints.