The fields IOBFLAG3 and IOBCSW have different meanings depending on the type of channel program and its format.

For format 0 CCW channel programs, these fields have the following format:

Figure 1. IOBFLAG3 and IOBCSW fields for format 0 channel program

For format 1 CCW channel programs, these fields have the following format:

Figure 2. IOBFLAG3 and IOBCSW fields for format 1 channel program

For zHPF channel programs, these fields have the following format:

Figure 3. IOBFLAG3 and IOBCSW fields for zHPF channel program

IOBFLAG3

This field is used by the system for format-0 CCW channel programs only.

IOBCMDA

The 24-bit ending CCW virtual address or zero for format-0 CCW channel programs. The ending CCW address points after the last executed CCW in your channel program. The ending address may be zero if either the system determined that the address was invalid or the last executed CCW was a CCW that was added by the system.

IOBCMD31

The 31-bit ending virtual address or zero for format-1 CCW channel programs and zHPF channel programs. For format-1 channel programs, the ending address points after the last executed CCW in your channel program. For zHPF channel programs, the ending address points to the TCW. The ending address may be zero if either the system determined that the address was invalid, or for CCW channel programs, the last executed CCW was a CCW that was added by the system.

IOBUSTAT

The device status (previously called unit status).

IOBCSTAT

The subchannel status (previously called channel status). If the ending address is zero or the subchannel status byte in the IOB (IOBCSTAT) shows any of the following errors: program check, protection check, channel data check, channel control check, interface control check, or chaining check, and your appendage determines that the ERP has not yet run, then let the ERP try to recover and do not modify IOBSTART. If the ERP has completed and one or more of these six bits is on or the address is zero, then the status of the channel program is not known.

IOBRESCT

The residual count for format-0 and format-1 CCW channel programs, which is the number of bytes not transferred in the last CCW. For zHPF channel programs, the residual count is four bytes and contained in the IOBE.

IOBFCXST

Used by the system.

IOBSESTA

The subchannel extended status for zHPF channel programs. The subchannel extended status further qualifies subchannel related errors defined in IOBCSTAT. Macro IHASESQ defines the different subchannel extended status values.