Endevor foreground compile ends with RC=0016 on STEP05 but no compile error

Products

• Endevor

Issue/Introduction

Endevor 18.1 foreground compile with COBOL 6.3 still fails after increasing TSO Logon REGION size from 8192 KB to 2096128 KB:

+++
          **                          PROCESSOR STEP INFORMATION                                                 **                  
          **                            STEP1A  .......RC=0000                                                   **                  
          **                            STEP02  .......RC=0000                                                   **                  
          **                            STEP03  .......RC=0000                                                   **                  
          **                            STEP04  .......RC=0000                                                   **                  
          **                          **STEP05  .......RC=0016  > MAXRC                                          **                  
          **                                                                                                     **                  
          *********************************************************************************************************                  
          *********************************************************************************************************                  
1PP 5655-EC6 IBM ENTERPRISE COBOL FOR Z/OS  6.3.0 P210514                 DATE 11/30/2021  TIME 13:16:31   PAGE     1      
...
...
-MESSAGES    TOTAL    INFORMATIONAL    WARNING    ERROR    SEVERE    TERMINATING                                                     
0PRINTED:     199          81            118                                                                                         
-* STATISTICS FOR COBOL PROGRAM IM31:                                                                                                
 *    SOURCE RECORDS = 60385                                                                                                         
 *    DATA DIVISION STATEMENTS = 14167                                                                                               
 *    PROCEDURE DIVISION STATEMENTS = 28177                                                                                          
 *    GENERATED COBOL STATEMENTS = 0                                                                                                 
 *    PROGRAM COMPLEXITY FACTOR = 28343                                                                                              
0END OF COMPILATION 1,  PROGRAM IM31,  HIGHEST SEVERITY 16.                                                                          
0RETURN CODE 16  
+++

The MESSAGES summary count for TERMINATING is zero. There is no IGY*-E or IGY*-U message and no compile error can be found.
There is also a panel error:
IEW4000I FETCH FOR MODULE IGYQCBE FROM DDNAME SYS00210 FAILED BECAUSE INSUFFICIENT STORAGE WAS AVAILABLE.
CSV031I LIBRARY ACCESS FAILED FOR MODULE IGYQCBE , RETURN CODE 14, REASON CODE 26110021, DDNAME SYS00210

Environment

Release : 18.0, 18.1

Component : Endevor Software Change Manager

z/OS 2.4, COBOL 6.3

Resolution

Compile returning RC=16 with no error messages match IBM APAR PH17872 ("Compiler ends RC=16 without a diagnostic..."): https://www.ibm.com/support/pages/apar/PH17872

===
PH17872: Compiler ends RC=16 without a diagnostic to suggest what needs correcting

A fix is available
Obtain the fix for this APAR.

APAR status
Closed as program error.

Error description
The compiler's optimizer and code generator is a rather large
module, with above the bar storage requirements, so there are
several sticking points to getting it up and running. Upon
failure of this bootstrap process, no message is being written
to increase REGION and/or MEMLIMIT.

Local fix
Increase REGION and MEMLIMIT.

Problem summary
****************************************************************
* USERS AFFECTED: All users of the Enterprise COBOL V6.1       *
*                 compiler who try to run the compiler in      *
*                 memory constrained environments.             *
****************************************************************
* PROBLEM DESCRIPTION: Incorrect output: The compiler listing  *
*                      may show the compiler ending with       *
*                      RC=16, without any accompanying error   *
*                      messages.                               *
****************************************************************
* RECOMMENDATION: Apply the provided PTF.                      *
****************************************************************
There are at least two memory constraint conditions which can
cause the compiler to fail to complete with RC=16 and no
explanatory error messages. Increase the REGION size and/or the
MEMLIMIT specifications to make sufficient storage available.

Problem conclusion
One of the conditions that causes this failure is the compiler
is unable to initialize the LE environment.  Existing compiler
messages IGYIN5294-U for V6.1 and IGYAS5294-U for V6.2 have
been updated and will be issued in this case.  In the other
case, the back end of the compiler fails to load due to
insufficient storage but clear messages identifying the problem
are already available in the JESYSMSG output for the job:
IEW4000I FETCH FOR MODULE IGYQCBE  FROM DDNAME STEPLIB  FAILED
BECAUSE INSUFFICIENT STORAGE WAS AVAILABLE.
CSV031I LIBRARY ACCESS FAILED FOR MODULE IGYQCBE , RETURN CODE
14, REASON CODE 26110021, DDNAME STEPLIB
IEF237I JES2 ALLOCATED TO CEEDUMP
===

As the IGYQCBE message was received the scenario matches APAR statement "In the other case, the back end of the compiler fails to load due to insufficient storage but clear messages identifying the problem are already available in the JESYSMSG output for the job: IEW4000I FETCH FOR MODULE IGYQCBE..." 
Therefore TSO Logon REGION size still appears to be too small for the compile to complete, but 2096128 KB is actually the largest allowed for TSO Logon REGION size (https://www.ibm.com/docs/en/zos/2.4.0?topic=pd-region-size). Customer agreed to discuss this further with IBM.