SQL0901: "SQL system error" and MCH2601: "Lock enforcement rules broken when trying to access object &1"

(Cross-posted to Midrange and RPG400 lists.)

We have a real mind-blower on our hands. We have an application which
submits several jobs to the job queue, which allows up to three jobs to run
simultaneously. The jobs run a program (the same program using different
data) which uses SQL *extensively*. SQL INSERTS are performed on tables
that exist in libraries that are unique to each job. DECLARE CURSORs are
defined with "FOR READ ONLY". No explicit locking (i.e., ALCOBJ) is used.

If the stars align correctly, we occasionally get an SQL0901, which is a
"SQL system error". The second-level text isn't much help except to suggest
that the job log should be looked at. (At the end of this post, I've pasted
the relevant part of the job log with "white space" removed to reduce line
wrapping.) I am usually able to replicate the error, and it seems to occur
when a particular segment of the program is being executed simultaneously by
two jobs. But nailing it down seems to be near impossible, given the lack
of information in the error and the job log. At this point, I am about to
add code to test for SQL0901 after every executable SQL statement, and
perform a dump with an identifying label. The MCH2601 message appears in
the job log just prior to the SQL0901, but I've not been able to find any
information on this message relevant to it being issued as a result of an
SQL error.

I searched the IBM Series i Support site for "MCH2601 SQL0901" (without the
double quotes) and got one hit. Unfortunately, it requires PartnerWorld
access, and it may be a few days before I can get the required company token
to be able to add myself to the company profile. (If anyone reading this
has PartnerWorld access and can send me the content from the result link, I
would be greatly appreciative.)

TIA,
Dan


MSGID TYPE SEV DATE TIME FROM PGM LIBRARY
INST TO PGM LIBRARY
MCH2601 Escape 40 03/23/10 11:40:11.412336 #cfochkr
000B10 QQQVAP QSYS
To module . . . . . . . . . : QQQVAP
To procedure . . . . . . . :
RESOLVE_SYSTEM_POINTERS
Statement . . . . . . . . . : 4204
Message . . . . : Lock enforcement rules broken when trying to access
object
&1.
MCH2601 Escape 40 03/23/10 11:40:11.414120 #cfochkr
000B10 QQQVALID QSYS
To module . . . . . . . . . : QQQVALID
To procedure . . . . . . . :
RESOLVE_SYSTEM_POINTERS
Statement . . . . . . . . . : 6700
Message . . . . : Lock enforcement rules broken when trying to access
object
&1.
CPF4204 Escape 50 03/23/10 11:40:11.414408 QQQQUERY QSYS
*STMT QQQQUERY QSYS
From module . . . . . . . . : QQQQUERY
From procedure . . . . . . : QQQQUERY
Statement . . . . . . . . . : 27564
To module . . . . . . . . . : QQQQUERY
To procedure . . . . . . . : QQQQUERY
Statement . . . . . . . . . : 27564
Message . . . . : Internal failure occurred in query
processor.
Cause . . . . . : A system failure has occurred in the query
processor
program. The query definition template number is 0. Recovery . . .
: See
the low-level messages. Correct any errors and try your request
again. If
the problem continues, report the problem (ANZPRB
command).
SQL0901 Diagnostic 50 03/23/10 11:40:11.414624 QSQRUN3 QSYS
*STMT QSQRUN3 QSYS
From module . . . . . . . . : QSQINS
From procedure . . . . . . : CLEANUP
Statement . . . . . . . . . : 24225
To module . . . . . . . . . : QSQINS
To procedure . . . . . . . : CLEANUP
Statement . . . . . . . . . : 24225
Message . . . . : SQL system error.
Cause . . . . . : An SQL system error has occurred. The current
SQL
statement cannot be completed successfully. The error will not
prevent
other SQL statements from being processed. Previous messages may
indicate
that there is a problem with the SQL statement and SQL did not
correctly
diagnose the error. The previous message identifier was CPF4204.
Internal
error type 3107 has occurred. If precompiling, processing will not
continue
beyond this statement. Recovery . . . : See the previous messages
to
determine if there is a problem with the SQL statement. To view
the
messages, use the DSPJOBLOG command if running interactively, or the
WRKJOB
command to view the output of a precompile. An application
program
receiving this return code may attempt further SQL statements.
Correct any
errors and try the request again.