System initialization program load (IPL) record

IPL records are recorded on the logrec data set to document system initializations. The system creates one IPL record for each initialization of the system. The IPL record provides a way of measuring the approximate time interval between the ending and reinitializing of the system.

Table 1. Format of the IPL record
Offset Size (bytes) alignment (bits) Field name Description
Dec Hex
0 (0) 1 CLASRC Class/Source:
    .1.1 ....   IPL record; type=X'50'.
1 (1) 1 OPSYS System/Release level:
    100. ....   OS/VS2.
    bits 3-7    
    0-1F   Release level 0-31.
2 (2) 4 SW1 Record switches:
    Byte 0    
    1... ....   More records follow.
    0... ....   Last record.
    .1.. ....   Time-of-day (TOD) clock instruction issued. Used in conjunction with date and time values at displacements 8 and 12.
    ..1. ....   Record truncated. (Not used for IPL record.)
    ...1 ....   Record created by MVS/SP Version 2, 3, or 4.
    .... 1...   TIME macro used.
    .... .xxx   Reserved.
    Bytes 1 and 2   Not used for IPL record.
    Byte 3   Incremental release number (alphanumeric) of operating system.
6 (6) 2   Not used for IPL record.
8 (8) 4 DATE System date when system was initialized.
12 (C) 4 TIME System time when system was initialized.
16 (10) 1 CPUSER Machine version code.
17 (11) 3 CPUSER1 Central processor serial number.
20 (14) 2 CPUMODEL Central processor machine model number.
22 (16) 2 MCELLNG Reserved.
        END OF STANDARD HEADER
24 (18) 1 SUBSYSID Device type or program that caused restart. See Table 2.
25 (19) 3   Not used for IPL record.
28 (1C) 2 REASON Alphanumeric reason for IPL. See Table 1.
30 (1E) 2   Reserved.
32 (20) 8 CHANASSN Reserved.
40 (28) 4 HIGHADDR Address of last valid byte of storage found at IPL time.
44 (2C) 4   Reserved.
48 (30) 8 LASTACT Last activity time and date from the time stamp record. When logrec is recording to log streams, the value in this field is zero.
Parent topic: Error recording on the logrec data set