IPL of z/OS system

Initial Program Load

System IPL

The first IPL after system installation
An IPL at which the PLPA is reloaded
An IPL after power-up
An IPL after a system crash

Initial Program Load. The initialization procedure that causes an operating system to start operations
Types of IPL

Cold Start:

Any IPL that loads (or reloads) the PLPA, but does not preserve VIO data set pages. The first IPL after system installation is always a cold start because the PLPA is initially loaded. Subsequent IPLs are cold starts when the PLPA is reloaded either to alter its contents or to restore its contents if they were destroyed.

Quick Start:

Any IPL that does not reload the PLPA and does not preserve VIO data set pages. (The system resets the page and segment tables to match the last-created PLPA.)

Warm Start:

Any IPL that does not reload the PLPA, but does preserve journaled VIO data set pages.

What happens at IPL time

LOAD SUCCESSFUL is a message from the IPL hardware/microcode. IPL does:

1) hardware system reset

2) optional memory clear

3) issues a basic READ (CCW op code 02) to the IPL device. It reads 24 bytes into absolute location 0. on disk, op code 02 is READ IPL, which seeks to cyl 0, trk 0 and reads the data portion of record 1. This is the IPL record on a disk initialized for IPL. On tape it just reads the first physical record on the tape (assuming the tape is rewound).

4) it continues the I/O by expecting 1 or 2 additional READ CCWs at absolute location 8 (part of the IPL record just read). On disk or tape this reads record 2, which can be quite large. It is possible for this record to contain more CCWs which are executed as part of the IPL, so it is possible for the IPL hardware function to load complex code into various parts of memory.

5) at this point, no instructions have been executed. If the I/O was successful, it loads a PSW from absolute location 0 (start of the IPL record) and starts execution.
If the I/O in steps 3/4 completes normally, you get LOAD COMPLETE.
Wait states are detected after the program begins executing (in the IPL program or NIP).

IPL PARMS

You can place the LOADxx member in one of the following system data sets:
SYSn.IPLPARM

SYS1.PARMLIB Consider placing LOADxx in the SYSn.IPLPARM data set.

During IPL, the system looks for LOADxx in the following order:

SYS0.IPLPARM through SYS9.IPLPARM on the IODF volume
SYS1.PARMLIB on the IODF volume
SYS1.PARMLIB on the sysres volume.

Do not create a SYSn.IPLPARM data set unless it contains the LOADxx member that is used to configure your system. When the system finds either SYSn.IPLPARM or SYS1.PARMLIB, it expects to find a LOADxx member in the data set. If the LOADxx member specified on the LOAD parameter is not in the data set, the system loads a wait state.

iplparm

IPL Problems

These are problems that some systems programmers have experienced. These problems are listed for reference only. Review the proper IBM documentation for any problems that you may encounter.

WAIT019
What happened for the wait019 was that SYS1.NUCLEUS was destroyed, but not in extents. I should have looked inside the SYS1.NUCLEUS as well outside. IEANUC01 should have been 608A10 in size, but was only about 7090 in size. Many other modules were hit also. Total size of SYS1.NUCLEUS was 13 cyls and should have been over 35 cyls. Just applied a lot of PTFs to the test system, OS/390 2.4.

Wait064
During IPL, after messages IEA549I SYSTEM CONSOLE 0B80 DEFINED AS MASTER CONSOLE

IEA168I VATLST00: SYSTEM DEFAULT USE ATTRIBUTE OF PRIVATE USED.
IEA304W SYSTEM WAIT STATE 800090064 DURING IEAVNPOE INITIALIZATION

The system is now dead. The system codes indicates a program check. wait064 09.

OW36941: A WAIT064 RC09 OCCURS DUE TO ABEND0C4 IN IEAVSWCS
ORIGINATING DETAILS: After removing a system from the sysplex, a WAIT064 rc9 (rc09) occurred when trying to IPL that system back into the sysplex. The WAIT064 occurred due to an ABEND0C4 in IEAVSWCS because IEAVN614 found an entry in the array mapped by IEAVN100 that had the CONRESET bit on, so IEAVN614 LINK'ed to IEECB825, who called IEAVSWCS, but UCMEPSTC and UCMEPSFC were both zero, so we're trying to unswitch a console that is not really switched. This entry in IEAVN100 is the 100th (or greater) entry in the array, but IEAVN600 only gets enough storage for 99 entries inthe array.

Wait088
Go to webpage

How the system finds that Master Catalog

There are two sources:
member LOADxx's SYSCAT, or SYS1.NUCLEUS(SYSCATLG)
SYSCATLG of SYS1.NUCLEUS will be used if the SYSCAT parameter is not included in the LOADxx member of SYS1.IPLPARM (or whatever).
The system will ask for a suffix xx to be appended to SYSCAT to form a member name in SYS1.NUCLEUS, if there's no SYSCAT statement in LOADxx, or IMSI was specified A, C, D, or P (ignore LOADxx's SYSCAT). If "Enter" is pressed, then the system will pick SYSCATLG. Or you can specify a different suffix. Probably, something unpleasant will happen if you press "Enter", but there's no SYSCATLG there.

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