Percolation for the same unit of work causes control to be given to one recovery routine after another for that same unit of work, which can be either a task or an SRB.
Percolation to an FRR always occurs from another FRR. If an FRR obtains locks that were not held when it was entered and then requests percolation, the system frees those locks before giving control to the next FRR. Also, if the percolating FRR requested that the system free any locks, the system frees these locks before giving control to the next FRR.
Percolation to an ESTAE-type recovery routine can occur from either an FRR or another ESTAE-type recovery routine. The environment in which an ESTAE-type recovery routine gets control does not vary regardless of whether the percolation request came from an FRR or another ESTAE-type recovery routine. Note that a recovery routine defined by the ESTAI parameter of the ATTACHX macro can choose either to percolate to a previous ESTAI routine (by setting a return code of 0 for the system) or to bypass further ESTAI recovery routine processing and continue with error processing (by setting a return code of 16 for the system).