VSE Header Record for SYSREC with CKD

Table 1 shows the format of the header record when IJSYSRC is on a count-key-data device.

Table 1. VSE CKD SYSREC Header Record
Offset Dec(Hex)	Size(bytes) Alignment(bits)	Field Name	Description
0(0)	2	CLASRC	Header record identifier. This field is set to X‘FF00’ unless critical data has been destroyed.
2(2)	4	LOWLIMIT	Address of low extent. Track address (in CCHH format) of first extent of SYSREC.
6(6)	4	UPLIMIT	Address of high extent. Track address (in CCHH format) of last extent of SYSREC.
10(A)	1	TRKSPER	Highest addressable track for each cylinder on the volume containing SYSREC.
11(B)	7	RESTART	Address of record entry area. Starting track address (in BBCCHHR format) for recording area on SYSREC.
18(12)	2	BYTSREM	Remaining bytes on track: number of bytes remaining on the track upon which the last record entry was written.
20(14)	2	TRKCAP	Total bytes on track. Number of bytes that can be written on a track of the volume containing SYSREC.
22(16)	7	LASTTR	Address of last record written. Track address (in BBCCHHR format) of last record written on SYSREC.
29(1D)	2	PUBNUM	Number of PUBS in the system.
31(1F)	2	EWMCNT	Warning count. Number of bytes remaining on early warning message track of SYSREC when 90% full point of data set is reached. When this is detected by a recording routine, it issues a message and turns on the early-warning-message switch at displacement 38.
33(21)	1	DEVCODE	Device code. Code indicating device type of system volume on which SYSREC resides: Code Device 01 2311 02 2301 03 2303 04 2302 06 2305 MOD 1 07 2305 MOD 2 08 2314 09 3330 and 3333 MOD 1 or 3350 operating in 3330-1 compatibility mode 0A 3340 and 3344 0B 3350 native mode 0C 3375 0D 3330 and 3333 MOD 11 or 3350 operating in 3330-11 compatibility mode 0E 3380 0F 3390
34(22)	4	EWMTRK	Early warning message track. Track address (in CCHH format) on which the 90% full point will be found.
38(26)	1	EWMSW	Switch byte:
	1... ....		90% full point message has been issued. This switch is turned on by recording routine detecting 90% full point and is turned off by IFCEREP1 when clearing SYSREC.
	.1.. ....		An emergency recording has occurred. This switch is turned on when the system terminates because SYSREC is full.
	..1. ....	FRAMES	Machine-check and channel-check frames exist on SYSREC.
	...x xxxx		Reserved.
39(27)	1	SFTYBYT	Check byte. Each bit in this field is set to 1 (X'FF'); used to check the validity of the header-record identifier.