Explanation
During system initialization, the system did not
initiate an I/O operation. The channel was not busy after the system
tried to store control and status information for the subchannel.
System action
The system enters wait state X'004'.
The system does not store the subchannel status word (SCSW).
Operator response
Report this problem to the system programmer.
System programmer response
You need to determine whether a device
or a path to the device caused the problem. The most likely path is
the last path used to access the device. Take the following steps:
- Using the hardware Alter/Display facility, read the
4-byte subchannel address in central storage at X'B8'. The
subchannel number is the last two bytes (at location X'BA')
of the 4-byte subchannel identification word at location X'B8'.
- Bring up the Device Configuration Display. Enter the 2-byte subchannel
number found in step 1. This displays
the device number, unit address, and the installed channel paths for
the selected subchannel number.
If there is only one channel path
to the device, there is no need for the system operator to continue
problem determination. Contact hardware support.
- It is likely that the failing path is the last path used. Display
subchannel status information. On CMOS-based processors, this is the
Analyze Subchannel Data display. Read the last path used mask (LPUM)
field to determine the last path used. The LPUM field consists of
8 bits. If bit n is on, then CHPIDn is the last path used. For example,
if the LPUM field shows B'01000000', bit 1 is on and the
CHPID1 field identifies the last path used.
- Bring up the CHPID menu and configure the last used channel path
offline.
- ReIPL the system.
- If the problem does not recur, you have identified the failing
path.
If the problem recurs and there are other paths to the device,
configure the other paths offline one by one until you have identified
the failing path. If this does not identify a failing path, the problem
is caused either by the remaining online path or by the device. Contact
hardware support.
Source
Input/output supervisor (IOS)