ATTACH FM header format

The format of the ATTACH FM header is defined in the following table.

Table 1. Attach FM header format
Byte	Bits	Name	Content
0		FMHL
1	0	FMHC
1	1-7	FMHT	B'0000101'
2-3		FMH5CMD	X'0202'
4	0-3	FMH5MOD
	4		Reserved
	5	ATTDP	Session Local Flag B'0' Not demand-paging B'1' Demand-paging
	6-7	ATTIU	Interchange Unit code B'00' Multiple chain B'01' Single chain B'10' Reserved B'11' Reserved
5		FMH5FXCT	Length of fixed-length parameters must be X'02'
6		ATTDSP	One-byte hexadecimal input value into a data stream profile. (IMS requires a value from X'00' to X'03' to select components 1-4 respectively. Value X'00', or component 1, is assumed if no ATTACH FM header is received while the Attach manager is in reset state.)
7		ATTDBA	Application data handling algorithm X'00' Undefined (Input only to IMS. IMS also assumes this as the default value if no ATTACH FM header is received while the attach manager is in reset state.) X'01' Variable length, variable blocked (input/output for IMS) X'02' Document subset of SCS (not supported by IMS) X'03' Card subset of SCS (not supported by IMS) X'04' A chain of RUs (input to/output from IMS) X'05' An RU (input only to IMS) X'06' to X'FF' Reserved
8-m		ATTDPN¹	Name of a process to be initiated. For an SNA-defined process, the DPN is a 1-byte, nongraphic hexadecimal character. Supported SNA processes are: X'01' SYSMSG X'02' SCHEDULER X'03' QMODEL The IMS processes are described under the ATTDPN parameter.
m+1-n		ATTPRN¹	Name of primary resource for the process being initiated
n+1-p		ATTRDPN¹	Name of suggested return process name
p+1-q		ATTRPRN¹	Name of suggested primary resource for the return process
q+1-r		ATTDQN¹	Name of queue to be associated with the attached process
r+1-s		ATTACC	Access code—Ignored by IMS.

Notes:

If the ATTDPN is set to SCHEDULER (X'02'), the remaining ATTACH parameters must not be specified. In this case, an equivalent for each of the asterisked parameters might occur in the concatenated SCHEDULER FM header. These SCHEDULER parameters are prefixed by SCD rather than by ATT, but follow the same definition and rules as those for ATTACH.