Subrecord Control Byte (SRCB)

The subrecord control byte (SRCB) is interpreted according to the RCB value, as shown in the following figures. The SRCB defines the record type (job header, data set header, job trailer, or user data record) plus SYSOUT carriage control type and user data spanning indicators (first, last, or middle segment). See Format of Data Records Containing Spanned Data for additional information on records containing spanned data.

Table 1. SRCB Definition - Part 1
RCB	SRCB
00	None
90	RCB of stream to be initiated
A0	RCB of stream to be initiated
B0	RCB of stream to be cancelled or rejected
C0	RCB of completed stream
D0	RCB of ready stream receiver
E0	Expected count - BCB sequence error (received count is in BCB)
F0	An identification character as follows: A = Reserved B = Network SIGNOFF C-H = Reserved I = Initial network SIGNON Must be only record in transmission buffer J = Response to initial network SIGNON Must be only record in transmission buffer K = Reset network SIGNON L = Accept (concurrence) network SIGNON M = Add network connection N = Delete network connection O-R = Reserved for IBM's use S-Z = Unused
91-94	Reserved

Note: F0 records are not compressed. Except where noted (I and J), multiple F0 records may be blocked in a single transmission. F0 records cannot be blocked with other records within a transmission.

Table 2. SRCB Definition - Part 2
RCB	SRCB
95-F5	Reserved
96-F6	Undefined
97-F7	Undefined
98-F8	NJE SYSIN control information as follows: 1000 0000 - Standard record 1100 0000 - Job header 1110 0000 - Data set header 1101 0000 - Job trailer 1111 0000 - Reserved 1111 0000 - Reserved for IBM's use
99-F9	NJE SYSOUT control information as follows: 10cc 0000 - Carriage control type as follows: 1000 0000 - No carriage control 1001 0000 - Machine carriage control 1010 0000 - ASA carriage control 1011 0000 - CPDS page mode records (with carriage control) 10cc ss00 - Spanned record control as follows: 10.. 0000 - Standard record (not spanned) 10.. 1000 - First segment of spanned record 10.. 0100 - Middle segment of spanned record 10.. 1100 - Last segment of spanned record 11cc 0000 - Control record as follows: 1100 0000 - Job header 1110 0000 - Data set header 1101 0000 - Job trailer 1111 0000 - Reserved for IBM's use
9A	Operator Command/Message (NMR) 1000 0000 (X'80')