The pfsctl function allows a PFS to provide error text for reason codes that are not supported by the kernel for display by the BPXMTEXT utility. The vfs_pfsctl command value is pfsctl_errortext (0xc000000b).

During initialization, the PFS declares a range of values for the high byte of the reason codes that it issues. To extract error text for a given reason code, the BPXMTEXT utility calls pfsctl, BPX1PCT. For reason codes not supported by the kernel, the LFS looks for a PFS that supports the high byte value and, if found, the LFS forwards the pfsctl call to that PFS for processing.