66D

Explanation
This system can issue this abend code
from three different areas in TSO/E: I/O services
REXX
CLIST processing.

A hexadecimal reason code identifies the error.  This code appears
either on user's terminal along with the abend notification, or in
the dump taken for the abend. Note: The reason code appears on the user's terminal as a four-byte
field. The rightmost two bytes contain the abend reason code. If these
two bytes are between X'000D' and X'0013', the leftmost
two bytes (if they are non-zero) contain the return code of the function
called by the module that issued the abend.For example, if the
reason code is X'0008000D', the abend reason code is X'000D',
and the return code of the function called by the module is X'0008'.

If the reason code is of the form X'zzzz0014', X'zzzz0064', X'zzzz0068',
or X'zzzz006C', it indicates a failure in IRXINIT while trying
to initialize the TSO/E TMP REXX environment.  If the rightmost two
bytes contain  X'0014', the leftmost two bytes contain the
IRXINIT reason code associated with IRXINIT return code  20. See the
topic about IRXINIT in z/OS TSO/E REXX Reference.
    If the rightmost two bytes contain X'0064' or X'0068',
indicating a system or user abend occurred in IRXINIT, the leftmost
two bytes contain the respective system or user abend code from IRXINIT.
If
the rightmost two bytes contain X'006C', the leftmost two
bytes contain the unexpected IRXINIT return code.  See codes X'14', X'64', X'68',
and X'6C' later in this information.

Code
Explanation
01
Recovery cannot be established.  This is an internal error. TSO
does not perform the requested function.
02
ECTIOWA contains an non-valid input stack address.
03
The input stack was in use by another task when re-serialization
was done.  I/O services, REXX, or CLIST processing encountered an error
in a multitasking environment.
04
An non-valid I/O service identifier was supplied by the caller.
This is an internal error.  TSO does not perform the requested function.
05
A input stack address is supplied in ECTIOWA but no stack exists.
06
No input stack exists.
07
No input stack exists, but one is being created by another program.
I/O service processing encountered an error in a multitasking environment.
Two tasks cannot create the first stack at the same time.
08
An abend X'0C4' occurred when validating user pointers or a pointer was set to zero.
09
The input stack is in use.
0A
An ECT was provided, but no stack exists.
0B
The ECTIOWA field does not contain the address of a valid stack.
0C
The user is trying to delete a stack which someone else is waiting
on.
0D
REXX is
unable to serialize on an internal resource.
0E
Unable to locate the REXX data stack.
0F
IRXESTK1 found an incorrect count of elements in the REXX data stack.
10
IRXESTK1 found an incorrect REXX data stack size.
11
IRXESTK failed when called by IRXESTK1.
12
IRXESTK failed to purge the number of stack elements requested
by IRXESTK1.
13
REXX stack
processing failed to release an internal REXX resource.
14
IRXINIT failed with return code 20 while trying to create the
TSO/E TMP REXX environment.
15
REXX variable
protection failed. This error can occur if sufficient storage is not
available to properly protect or unprotect variables when attempting
to invoke an authorized command or program under REXX. If this error occurs, try
changing your TSO/E PROFILE setting to PROFILE VARSTORAGE(HIGH). You
might also try using a larger REGION size when logging onto TSO/E.
16
The MARKTERM function of IRXESTK failed. While processing the
data stack, TSO I/O services encountered an error.  TSO does not perform
the requested function.
17
The DROPTERM function of IRXESTK failed. While processing the
data stack, TSO I/O services encountered an error.  TSO does not perform
the requested function.
18
The PULL function of IRXESTK failed. While processing the data
stack, TSO I/O services encountered an error.  TSO does not perform
the requested function.
19
The input stack size limit was exceeded.
1E
The REXX storage
manager was passed a control block that is not valid.
1F
The REXX storage
manager was requested to free storage for a control block that is
not valid.
20
The REXX storage
manager could not allocate storage from the requested control block
due to an internal error.
21
The REXX storage
manager could not free storage for the requested control block because
the storage was freed previously.
22
The REXX storage
manager could not free the storage because the storage tree is not
valid.
23
The REXX storage
manager could not free the storage because the storage tree is not
valid.
24
The REXX storage
manager could not allocate the requested storage. The tree used to
manage the storage has an incorrect format.
25
The REXX storage
manager could not allocate the requested storage. An internal tree-management
routine failed.
26
The REXX storage
manager could not allocate the requested storage. The tree was determined
to be not valid after storage allocation occurred.
27
The REXX storage
manager could not allocate the requested storage. The tree was determined
to be not valid after storage allocation occurred.
28
The REXX storage
manager could not assign the new extent.
29
The REXX storage
manager could not obtain additional storage from the main REXX storage manager
control block.
2A
The REXX storage
manager determined that a tree is not valid.  An incorrect control
block was present at the top of the tree.
2B
The REXX storage
manager determined that a tree is not valid.  An incorrect control
block was passed.
2C
The REXX storage
manager determined that a tree is not valid.  An inner vertex appeared
in place of the top of the tree.
2D
While invoking an internal routine, the REXX storage manager determined
that no dynamic storage was available.
2E
The REXX storage
manager could not obtain the requested storage.
2F
The REXX storage
manager could not free the requested storage.
30
Module IGX00043 was invoked with parameters that were not valid.
TSO/E I/O services encountered an internal error. TSO does not perform
the requested function.
31
A TSO/E service that requires a TSO/E environment was invoked
in a non-TSO/E environment.
3C
The QUEUED function of IRXESTK failed. While processing the data
stack, TSO I/O services encountered an error. TSO does not perform
the requested function.
40
GETMAIN failure. This error can occur if sufficient storage is
not available in the CLIST or Authorized REXX variable pool. If this error
occurs, try changing your TSO/E PROFILE setting to PROFILE VARSTORAGE(HIGH). 
41
Stack serialization token has wrapped.
42
The token which was associated with the top stack element has
changed. This means that the stack has been modified while the lock
was released.
43
A TSO/E Service Routine detected a serialization error with the
ALTLIB or VLF environment.
44
The user is trying to OPENFILE a dataset which is marked EXECUTE-ONLY.
45
The user is trying to submit a member of a dataset which is marked
EXECUTE-ONLY.
46
The user is trying to execute a CLIST from a dataset which is
marked EXECUTE-ONLY.
47
The user invoked the TSO/E environment service with a bad parameter
list.
48
The user tried to invoke the TSO/E environment service on an incorrect
version of TSO/E.
49
The user attempted to run an authorized command or program.  This
is not supported in the TSO/E environment created by the TSO/E environment
service.
4A
The user attempted to attach the TSO/E TMP routine (IKJEFT01)
while in a dynamic TSO/E environment.
4B
REXX output
processing failed in a TSO/E environment.  No command processor parameter
list (CPPL) was available.
4C
REXX output
processing failed in a TSO/E environment.
4D
TSO/E has detected an overlay condition while reading a member
from a concatenated data set.  One possible reason for this overlay
condition is the concatenation of data sets with unlike RECFM specifications.
4E
TSO/E was invoked in a Web client environment, but JSON message
processing did not start.
4F
TSO/E was invoked in a Web client environment, but a severe error
occurred during normal TSO/E processing.
50
The user entered the REXX immediate command HE in order to halt execution
of the current REXX exec.
This abend does not represent an error condition.
51
Incorrect key or state at invocation.
52
An ESTAE environment could not be established.
53
Caller is not at the expected operating system level (OS/390® Release 3 or higher).
54
Invalid request passed from caller.
60
The ENVTABLE_HEADER pointer is zero, and a valid REXX ENVTABLE
address cannot be obtained.
61
The ENVTABLE_ENTRY pointer for the terminating REXX ENVBLOCK does
not point within the bounds of the ENVTABLE from entry two through
the end of the ENVTABLE.
62
The CHAIN_LOCK pointer for the terminating REXX ENVBLOCK does
not point within the bounds of the ENVTABLE from entry two through
the end of the ENVTABLE.
64
IRXINIT failed with return code 100 while trying to create the
TSO/E TMP REXX environment.
68
IRXINIT failed with return code 104 while trying to create the
TSO/E TMP REXX environment.
6C
IRXINIT failed with an unexpected return code while trying to
create the TSO/E TMP REXX environment.
Note: If you are not able to locate the abend reason
code in the preceding table, see Explanation at
the beginning of the explanation for 66D abend code.

System action
The action of the system varies depending on the
error and on the level of ESTAE that receives control.  In all cases,
the TSO/E or REXX function
is not performed.  However, for a TSO/E CLIST or a REXX exec, a retry might be attempted
following the statement that encountered the error.  In most cases,
the TSO/E READY mode is reinstated.  If the abend occurs during TSO/E
logon, the user must log on again. Code
System Action
02 - 0B
An SVC dump is not taken for the abend.
0D - 13
See 1  at the beginning of the
description of abend code 66D. An SVC dump is not taken for the abend.
14 - 19
An SVC dump is not taken for the abend. For 14, see 2  at the beginning of the description of
abend code 66D.
64
See 2 at the beginning of  the
description of abend code 66D. An SVC dump is not taken for the abend.
68
See 2  at the beginning of  the
description of abend code 66D. An SVC dump is not taken for the abend.
6C 
See 2  at the beginning  of  the
description of abend code 66D. An SVC dump is not taken for the abend.

System programmer response
If no fix exists, contact the IBM® Support Center.

Programmer response
Try rerunning the REXX exec or re-invoking the TSO/E
function. The error may have been due to a temporary condition (such
as insufficient storage), and your job may succeed on a second attempt.
If
the error is severe, the TSO/E session may need to be restarted. Code
Response
02
Check the validity of the I/O service parameter list and the command
processor parameter list (CPPL).  Verify that the ECT address in both
of these parameter lists is correct, that is, the ECT address supplied
to a command processor is in fact, in the CPPL.
05
Check the validity of the I/O service parameter list and the command
processor parameter list (CPPL).  Verify that the ECT address in both
of these parameter lists is correct, that is, the ECT address supplied
to a command processor is in fact, in the CPPL.
06
Wait until the stack is created by the terminal monitor program
(TMP) initialization function before calling this service, or use
the stack-create service.
08
Verify that all addresses in the I/O service parameter list (and
the IKJCT441 parameter list if applicable) are correct.
0B
Provide a valid stack address in the ECTIOWA.  The stack address
may be obtained from the ECT provided by the ECT pointed to from the
CPPL or the stack-create service.
14
IRXINIT failed with return code 20 (X'14') while trying
to initialize the TSO/E TMP REXX environment. The complete 4-byte
reason code is of the form X'zzzz0014'. The zzzz portion
is the IRXINIT reason code documented in the topic about IRXINIT in z/OS TSO/E REXX Reference,
which further describes the  meaning of IRXINIT return code 20.  The
REXX environment is not initialized.  Message  IRX0900E or IRX0901E,
issued to the console, usually accompany this error. If your installation
has replaced a parameters module,  verify that the correct module
was called during REXX initialization.  Example

00150014
IRXINIT completed with return code X'14', reason code X'15':
a module cannot be loaded. To locate the module name, look for message
IRX0901E issued to the console.
 001B0014
IRXINIT completed with return code X'14', reason code X'1B':
the wrong number of parameters. Message IRX0900E might also be issued.

15
The READY state resumes; retry the TSO function.
19
Log off from TSO/E and log back on.  If the problem occurs again,
check your programs that were running around the time of the abend.
Any programs that perform input stack operations using the stack service
routine should be examined for possible looping conditions.
31
Rerun the program in a TSO/E environment or address space.
44
Obtain READ access from the owner of the dataset. The user cannot
OPENFILE a dataset marked EXECUTE-ONLY.
45
Obtain READ access from the owner of the dataset. The user cannot
submit a member from a dataset marked EXECUTE-ONLY.
46
Obtain READ access from the owner of the dataset. The user cannot
run CLISTs from a dataset marked EXECUTE-ONLY.
47
See z/OS TSO/E Programming Services 
for information on invoking the TSO/E environment service.  Correct
the error and invoke the TSO/E environment service again.
48
Make sure the installation has the proper version of TSO/E installed.
49
Remove the TSO/E authorized command or program that you tried
to run.
4B
If you are using the IRXEXEC programming service, provide a CPPL
and retry the operation.
4C
Ensure that the TSO/E I/O services are available in the address
space.
4D
Invalid record length found. One possible reason is the concatenation
of FB and VB data sets being used for CLIST input.
4E
Ensure the code page, character set,  and any additional logon
options are correctly specified before starting TSO/E.
4F
Ensure there is a valid logon procedure in use that invokes only
IKJEFT01.
64
IRXINIT failed with return code 100 (X'64') while trying
to initialize the TSO/E TMP REXX environment. This indicates that
IRXINIT encountered a system abend.  The complete 4-byte reason code
is in the form X'zzzz0064' where zzzz is
the hexadecimal abend code of the system abend.  If necessary,
set a SLIP COMP=zzz to get a dump
for the abend zzz in IRXINIT, where zzz represents
the rightmost  three hex digits of the system abend code.

68
IRXINIT failed with return code 104 (X'68') while trying
to initialize the TSO/E TMP REXX environment. This indicates that
IRXINIT encountered a user abend.  The  complete 4-byte reason code
is in the form X'zzzz0068' where zzzz is
the hexadecimal abend code of the user abend  in IRXINIT.  If necessary,
set a SLIP COMP=Udddd to get a
dump for the user abend in IRXINIT, where dddd are
the decimal digits of the user abend code. That is, hex code zzzz converted
to decimal dddd.

6C
IRXINIT failed with an invalid non-zero return code while trying
to initialize the TSO/E TMP REXX environment. The complete 4-byte
reason code is in the form X'zzzz006C' where zzzz is
the hexadecimal IRXINIT return code.If necessary, set a SLIP
COMP=66D to get a dump for this abend.

Source
Time Sharing Option Extensions (TSO/E)