DB2 FOR LUW / DB2FORLUW / B10 - DB2

A routine ( procedure or function ) can fail with error SQL1646N 
because the fenced user ID does not have permissions to attach 
to the shared memory used for db2fmp <-> db2sysc communication. 
 
The error will not necessarily reflect this problem as the error 
can have different causes. 
 
The db2diag.log will report this message : 
 
EDUID   : 117                  EDUNAME: db2agent (SAMPLE) 0 
FUNCTION: DB2 UDB, routine_infrastructure, 
sqlerInvokeFencedRoutine, probe:1220 
MESSAGE : ZRC=0xFFFFF992=-1646 
          SQL1646N  A routine failed because the fenced user ID 
cannot access 
          required files in the sqllib directory or other 
instance or database directories. 
 
The problem is that the main DB2 process will have allocated a 
shared memory segment for db2fmp communication but due to 
operating system settings, this segment might be split across 
multiple segments. The db2diag.log also reports this : 
 
FUNCTION: DB2 UDB, SQO Memory Management, 
sqloGetSharedMemoryFromOs, probe:2026 
DATA #1 : <preformatted> 
Unable to allocate 56832 MB in a single segment, 14 segments 
were required. 
Possible causes may include an improper setting for the shmmax 
Linux kernel 
tuneable, or a system-wide limit on the segment size. 
 
After allocation of this memory, the correct permissions should 
be set so that the fenced user id can access these, however this 
is incorrectly only done for the first segment that was 
allocated. The apar fix will ensure that all segments have the 
right permissions. 
 
Note that this problem is likely to surface since V11.1 M1 FP1 
due to a changed memory allocation strategy for the FMP memory 
segment. This change may have too much impact and expose 
problems like the problem documented in this apar. 
Hence, the change will be altered by apar IT19471.

**************************************************************** 
* USERS AFFECTED:                                              * 
* Users of DB2 version 11.1                                    * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Update to V11.1 M1 FP2 or higher.                            * 
****************************************************************

Set the FMP memory segment size to the original 256MB amount 
 
   db2set DB2NTMEMSIZE=APLD:268435456 
 
This requires recycling the instance (db2stop force; db2start) 
 
While the documentation indicates that DB2NTMEMSIZE is valid 
only for the Windows platform, 
it is also effective for UNIX platforms on the DB2 level 
vulnerable to APAR IT19471 (DB2 v11.1 mod 1 fix pack 1). 
Its use is not generally supported on UNIX platforms, and the 
setting should be removed upon upgrading to a level containing 
APAR fix for apar IT19471.

DB2 Version 11.1 Mod 2 Fix Pack 2 for Linux, UNIX, and Windows
 Db2 Version 11.1 Mod2 Fix Pack2 iFix001 for Linux, UNIX, and Windows
 Db2 Version 11.1 Mod2 Fix Pack2 iFix002 for Linux, UNIX, and Windows
 Db2 Version 11.1 Mod 3 Fix Pack 3 for Linux, UNIX, and Windows
 Db2 Version 11.1 Mod3 Fix Pack3 iFix001 for Linux, UNIX, and Windows
 Db2 Version 11.1 Mod3 Fix Pack3 iFix002 for Linux, UNIX, and Windows
 

Update to V11.1 M1 FP2 or higher.

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

27.02.2017
23.06.2017
23.06.2017