204

Explanation
An error occurred during Allocation processing.
A reason code appears in bits 36 through 51 of the wait state PSW
and explains the error:Code
Explanation
0000
During system initialization, the system found an eligible devices
table (EDT) identifier specified in the LOADxx parmlib member that
does not exist in the I/O definition file.
0001
During system initialization the system could not build the AGT.
0002
During system initialization, the system could not build the TSRA.
0003
During system initialization or ABEND recovery processing, the
system could not attach or reattach the Tape Switch work task.
0004
During system initialization, the system could not join the sysplex.
0005
The Tape Switch work task encountered too many errors.
0006
ATS initialization error.
0007
IEFHBPDB task failed. 
0008
During ALLOCAS initialization, the system could not obtain storage
for device information. The amount of storage on the GETMAIN request
depends on the number of devices in the configuration and the maximum
number of users determined by the MAXUSER value in the IEASYSxx parmlib
member. The GETMAIN failure may occur if these numbers are large,
so consider reducing the number of devices in the configuration and
/ or the MAXUSER value. For a detailed description of MAXUSER, RSVNONR,
and RSVSTRT in IEASYSxx, refer to z/OS MVS Initialization and Tuning Reference.
0040
IEFHBPDC could not be attached.

System action
The system enters a non-restartable wait state X'204'.

System programmer response
If the reason code is X'0000',
check that the EDT identifier specified in LOADxx exists
in the I/O definition file. If filtering keywords such as HWNAME,
LPARNAME, and VMUSERID are used, verify that they allow the desired
IODF to be found. ReIPL the system.
If the reason code
is X'0008', search problem reporting databases for a fix
for the problem. If no fix exists, take a stand-alone dump and contact
the IBM® Support Center. If a
new IODF configuration is used for IPLing, return to the previous
configuration in the interim. Try to reduce the number of devices
in the configuration and/or use a smaller MAXUSER value in IEASYSxx.
For
all other reason codes, search problem reporting databases for a fix
for the problem. If no fix exists, contact the IBM Support Center.

Source
Allocation