You can activate an FRR from either another FRR or from an ESTAE-type recovery routine. When activating an FRR from an ESTAE-type recovery routine, the ESTAE-type recovery routine must have acquired a lock after being entered, or the FRR must be an EUT FRR.
You should activate an ESTAE-type recovery routine only from an ESTAE-type recovery routine. IBM® recommends you do not activate an ESTAE-type recovery routine from an FRR, because it might not get control in the correct order.
Any recovery routine activated from a recovery routine is called a nested recovery routine. A nested recovery routine can retry provided the error for which it gets control is retryable. Whether the nested recovery routine can retry is independent of whether the recovery routine that activated the nested recovery routine can retry. For example, a recovery routine might get control for a non-retryable error. The recovery routine itself might encounter an error for which its recovery routine (the nested recovery routine) gets control and can retry. The retry routine from a nested ESTAE or ESTAEX recovery routine runs under the RB of the ESTAE-type recovery routine that activated the nested recovery routine.
Nested FRRs do not have access to their owning FRR's SDWA or 304-byte work area. The system makes a temporary copy of these areas and re-uses the original SDWA and work area when giving control to the nested FRR. Nested FRRs do have access to their owning FRR's 24-byte parameter area.