Input/Output Block Common Extension (IOBE) Fields

You can construct an IOB common extension (IOBE) block to receive extended error information or to control the level of error recovery procedure (ERP) processing. To provide an IOBE, set IOBCEF in IOBFLAG4 on and set the IOBE address in register 0 when you issue EXCP or EXCPVR. (The IOBE is mapped by the IOSDIOBE macro).

Set reserved bytes to X'00'. The IOBE can reside above or below 16MB virtual.

Start of change The constant IOBELNTH is set to the length of the IOBE and should be used when obtaining and clearing storage. In addition, the constant IOBEEND represents the end of the IOBE. End of change

Figure 1. Format of an IOBE, mapped by the IOSDIOBE macro

Table 1. IOBE Structure Mapping
Offset	Length or Bit Pattern	Name	Description
0 (X'0')	4	IOBEID	Eye catcher ("IOBE")
4 (X'4')	1	IOBEVERS	Version number (X'01')
5 (X'5')	1	IOBEFLG1	Reserved.
6 (X'6')	1	IOBEFLG2	Flag field 2. Set by issuer of EXCP or EXCPVR.
	1... ....	IOBEMIDA	The channel program might have one or more CCWs that has the MIDA (modified indirect data addressing) bit on and point to a MIDAL (modified indirect addressing list). Supported only for EXCPVR requests. This bit must set to zero if you are using a zHPF channel program.
	.1.. ....	IOBEP	The user allows unlimited prefetching of CCWs. (Unlimited prefetching of the IDAWs, MIDAWs, and data associated with the currrent or prefetched CCW is always allowed.) If zero, no prefetching is allowed, except in the case of data chaining on output, where prefetching of one CCW describing a data area is allowed. Prefetching of CCWs applies only for FICON® channels. It has no effect on Enterprise Systems Connection (ESCON®) or parallel channels. This bit applies to EXCPVR; EXCP always uses unlimited prefetching. This bit must set to zero if you are using a zHPF channel program.
	..1. ....	IOBECPNM	The user guarantees that the channel program will not be modified during execution other than to add CCWs at the end. This bit is supported only for EXCPVR requests. EXCP requests that do not run in an authorized V=R address space cannot be modified during execution. This bit must set to zero if you are using a zHPF channel program.
	...1 ....	IOBEEIDA	Any IDAWs are eight bytes each and point to 4096-byte boundaries with the possible exception of the first IDAW in each list. Currently supported only on direct access storage device (DASD) and on IBM-supplied cartridge tape devices. Bit UCBEIDAW in the UCB tells you whether the device supports 64-bit IDAWs. Supported for EXCP and EXCPVR and for format-0 and format-1 channel programs. Not currently supported in VIO. This bit must set to zero if you are using a zHPF channel program.
	.... 1...	IOBEPCIS	PCI synchronization. Channel must synchronize after the next CCW following a PCI (at CCW+8). Supported for EXCPVR only if IOBEP is on. Not supported in VIO. EXCP requests never require PCI synchronization. This bit must set to zero if you are using a zHPF channel program.
	.... .1..	IOBNORWS	No read/write synchronization. The channel should not synchronize on read/write transitions. User guarantees that the reads and writes are from different areas. Always supported for EXCP. Supported for EXCPVR only if IOBEP is on. This bit must set to zero if you are using a zHPF channel program.
	.... ..1.	IOB2CSWS	Two channel status words. If an error occurs where the control unit is executing ahead of the channel, the system returns two ending CCW addresses. The second ending CCW address is in the IEDB. Always allowed for EXCP. Supported for EXCPVR only if IOBEP is on. If this bit is off when the control unit has an error when executing ahead of the channel, the system simulates an invalid ending CCW address. This bit must set to zero if you are using a zHPF channel program.
	.... ...1	IOBEFMT1	Channel program is format-1 CCWs and IOBSTART contains a 31-bit address. This bit also causes the system to use IOBESIOC instead of IOBSIOCC and for the ending CCW address to be in IOBCMD31 instead of the three bytes in IOBCMDA. Supported for both EXCP and EXCPVR requests. This bit must set to zero if you are using a zHPF channel program.
7 (X'7')	1	IOBEERPM	Mask indicating the functions the ERP is allowed to perform.
	1.......	IOBEPMSG	User allows basic error recovery procedures (ERP) recovery and permanent error messages that do not require interaction with the system or an operator. See "Requesting Different Levels of ERP Processing" on page 87.
	.xxx xxxx		Reserved.
8 (X'8')	4	IOBEUSER	Address field for user use.
8 (X'8')	4	IOBEUPTR	Character field for user use.
12 (X'C')	4	IOBEIEDB	Zero or address of IEDB if you want extended error information. For more information see, Requesting Extended Error Information.
16 (X'10')	1	IOBEFLG3	Flag byte 3.
	1... ....	IOBENSER	Set by user to allow the device to bypass the channel program extent collision checking. Extent range enforcement remains active. Meaningful only if the DASD supports it; has no effect otherwise. Can improve performance on IBM® 2105 Enterprise Storage Server™ and newer DASD control units when using multisystem access or multiple parallel access volumes (PAV).
	.1.. ....	IOBENVAL	Set by user to allow the device to bypass the validation checking of the parameters on define extent and locate record commands. Extent enforcement remains active; meaningful only if the DASD device supports it, has no effect otherwise. Can improve performance on IBM 2105 Enterprise Storage Server® and newer DASD control unitswhen using multisystem access or multiple parallel access volumes (PAV).
	..1. ....	IOBEDSMC	Set by user to disable streaming mode control. This bit must set to zero if you are using a zHPF channel program.
	...1 ....	IOBEIOT	If the user sets this to 0, IOBETIME applies to the request only while the request is active. If this is 1, IOBETIME applies while the request is queued or active.
	.... 1...	IOBEDCWOffsetValid	For zHPF channel programs, the DCW offset in IOBEDCWOffset is valid.
	.... .1..	IOBEResCountValid	For zHPF channel programs, the residual count in IOBEResCount is valid.
	.... ..xx		Reserved.
17 (X'11')	1	IOBESIOC	Same format as IOBSIOCC. Valid only if IOBEFMT1 is on.
18 (X'12')	1	IOBETIME	Time limit. If this value is non-zero, it is the number of seconds the user allows the request to take. Has an effect if the DEBACCS field shows the DCB is open for input. There will be no message or error recording due to reaching the limit. Bit IOBEIOT specifies what time is measured.
19(X'13')	1	IOBEFLG4	Flag byte 4.
	1... ....	IOBEZHPF	This is a zHPF channel program. This bet must be set to zero for CCW channel programs.
	.xxx xxxx		Reserved.
20(X'14')	4	IOBEResCount	For zHPF channel programs, this field contains the residual count. This field is valid only if IOBEResCountValid is on.
24(X'18')	2	IOBEDCWOffset	For zHPF channel programs, this field contains the offset within the TCA of the DCW that was partially or completely executed. If the channel program could not be completed, this offset identifies the DCW for which processing could not be completed. This field is valid only if IOBEDCWOffsetValid is on.
26(X'1A')	1	IOBEDDPC_RC	For zHPF channel programs, this field contains the device detected program check reason code. This field is valid only when the subchannel status indicates a program check and the subchannel extended status indicates a device dependent program check. The reason codes are documented in z/Architecture® Principles of Operation.
27(X'1B')	1	IOBEDDPC_RCQ	For zHPF channel programs, this field contains the first byte of the device detected program check reason code qualifier. This field is valid only when the subchannel status indicates a program check and the subchannel extended status indicates a device dependent program check. The reason code qualifiers are documented in z/Architecture Principles of Operation.
28(X'1C')	1	IOBERCOD	The I/O completion reason code. This is the second byte of the completion code for the channel program. The system also places this code in the second byte of the event control block when the channel program is posted complete. The reason codes applicable to EXCP or EXCPVR and their meanings are listed in Event Control Block (ECB) Fields.
29(X'1D')	19		Reserved.