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Database hangs when a 4GL program using _lock locks up.

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Information

 
EnvironmentProduct: Progress
Version: 9.x
Product: OpenEdge
Version: 10.x
OS: All supported platforms
Question/Problem Description
A 4GL program querying the _Lock VST table hangs.
Database hangs and all users freeze.

Stack trace from _progres on Solaris reads:

poll
select
select
latSleep
latlkmux
vstLockFetch
rmFetchVirtual
Steps to Reproduce
Clarifying Information
Error Message
Defect/Enhancement NumberDefect OE00111869 / PSC00158220
Cause
Under specific conditions, if a client hangs while reading the _Lock VST table, the whole database may hang.
Resolution
None at this time.
Workaround
Consider using a more efficient table: _Userlock:
  • It's result set is much smaller because it limits the number of locks per user instead of a scan of the entire lock table.
  • _UserLock reports the first 512 lock entries for a particular user with "one request" to the lock subsystem
  • _UserLock provides a snapshot per user per _user-lock record and not a changing picture as each _lock is per
    lock.
  • The following restriction applies: if a single user has more than 512 locks, they will be missing in the _userlock array.
  • For a code example and improvements in OpenEdge 11.6 refer to Article 000021994, What is the Record locking table _UserLock   
Notes

To obtain a stacktrace from the hung process on UNIX:


kill -16 PID >> pid.txt (most UNIX's)
or
pstack PID >> pid.txt (on Solaris)
Complete stack trace:

poll
select
select
latSleep
latlkmux
vstLockFetch
rmFetchVirtual
dsmRecordGet
slrmget
dbrmget
dbqry
proqry
profnd
fdfnd
bfFindRow
rnbfnxtDoit
rnbfnxtBody
rnbfnxt
rnexec_entry
rninterpret
rnrq
main
cabc _start
Attachment 
Last Modified Date4/21/2017 1:09 PM
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