PFS abnormal ends

If the user address space or task terminates while actually running in the PFS code for a PFS interface operation, or if the PFS code itself fails, an MVS™ abnormal end is generated for each affected task. The MVS system then usually runs the FRR and ESTAE recovery exits.

If the PFS does not have recovery established, the vn_recovery operation is available to allow the PFS to run its recovery processing as an exit from the LFS's ESTAE. See the description of vn_recovery and vfs_recovery that follows this list.
If the PFS needs its own special recovery, it must establish an FRR or ESTAE on each entry from the LFS.
If task-level recovery is bypassed by MVS, the end-of-memory (EOM) resource manager established by z/OS UNIX is run. It ensures that the PFS has a last chance to clean up by calling vfs_recovery. See the next topic on vn_recovery and vfs_recovery.

vn_recovery and vfs_recovery are called to permit a PFS to recover resources when a user request ends abnormally, or when the user's address space enters EOM processing while a request to that PFS is active. This works as follows:

On every VFS and vnode operation, the LFS makes an 8-byte recovery area available to the PFS. This field is in the PFS's primary address space, not in the user's address space. Its address is in the OSI.
The PFS should set this field soon after entry, or when it has resources that need protection. The field is used for recovery information, or for the address of a recovery structure that is not in the user's address space.
The PFS clears the field on exit. The LFS also clears the field as soon as the PFS returns, as it has meaning only during a call, and presumably the area it points to is no longer valid. The PFS should clear the field so that it cannot be invoked with bad data if the user is canceled after the PFS has returned, but before the LFS can zero out the field.
If an abnormal end occurs and the LFS ESTAE routine finds this area to be nonzero, the area is passed to the PFS with a call to vn_recovery and cleared after this call.
See vn_recovery — Recover resources after an abend for more details.
If the EOM resource manager for a user address space finds this area to be nonzero, the area is passed to the PFS with a call to vfs_recovery. This can happen only for an abnormal end that bypasses normal ESTAE processing, or when an address space is canceled during ESTAE processing.
See vfs_recovery — Recover resources at end-of-memory for more details.
The PFS uses the information that is stored in the area during vn_recovery or vfs_recovery to clean up whatever was in progress at the time of the interruption.

The PFS can establish its own MVS dynamic resource managers if it must perform special recovery for a user or z/OS UNIX task or address space termination. This is not recommended, however, because severe performance degradation occurs if these resource managers have to be set up and removed on every operation.