[DERBY-4917] zero byte dbex.lck file can cause dual boot warning saying Severe and non-recoverable corruption can result and may have already occurred.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 10.1.2.1
• Component/s: Store
• Labels: derby_triage10_8

Environment

z/OS

E205{S000EKA}> java -version
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build pmz31devifx-
20100215 (SR
11 FP1 ))
IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 z/OS s390-31 j9vmmz3123ifx-
20100127a
 (JIT enabled)
J9VM - 20100122_52103_bHdSMr
JIT - 20091016_1845ifx1_r8
GC - 20091026_AA)
JCL - 20100215

Derby 10.2.2.1 - (815839)

• Urgency: Normal
• Issue & fix info: Workaround attached
• Bug behavior facts: Seen in production
• Assignee: Unassigned
• Reporter: Katherine Marsden
• Created: 24/Nov/10 23:39
• Updated: 25/Nov/13 12:51

Description

User reports the following warning booting Derby 10.2 with JDK 1.5 SR11 FP1 on z/OS.

ij> connnect 'jdbc:derby:wombat';
IJ ERROR: Unable to establish connection
ij> connect 'jdbc:derby:wombat';
WARNING: Derby (instance c013800d-012c-8027-19b4-000000037b18) is attempting to
boot the database <snip dbname > even though Derby (instance c0
13800d-012c-74ae-07c3-0000000af3f0) may still be active. Only one instance of D
erby should boot a database at a time. Severe and non-recoverable corruption can
result and may have already occurred.

The dbex.lck file is zero length. The code seems to indicate in DirFile4.getExclusiveLock() that a zero length dbex.lck file is possible if the product is booted with less than JDK 1.4 and Derby should show the warning under these circumstances, but investigation shows that even if the dbex,lck file is removed it is recreated with zero length using JDK 1.5. So there seem to be two issues.
1) dbex.lck is somehow getting created with zero length with JDK 1.5 on this machine with JDK 1.5 SR11 FP1.

2) We have this logic pertaining to JDK 1.3.1 in the product that probably can be removed and perhaps masks a real exclusive locking problem that perhaps should issue an Error rather than a warning if the file cannot be created with 4 bytes as expected.

I can mimic the Warning on my system with a manufactured zero length dbex.lck file e.g.
mv dbex.lck dbex.lck.orig
touch dbex.lck
java org.apache.derby.tools.ij
ij version 10.2
ij> connnect 'jdbc:derby:wombat';
IJ ERROR: Unable to establish connection
ij> connect 'jdbc:derby:wombat';
WARNING: Derby (instance c013800d-012c-8027-19b4-000000037b18) is attempting to
boot the database /u/kmarsd/repro/lockwarn/wombat even though Derby (instance c0
13800d-012c-74ae-07c3-0000000af3f0) may still be active. Only one instance of D
erby should boot a database at a time. Severe and non-recoverable corruption can
result and may have already occurred.

I see the same warning with 10.7.

Possible workaround for eliminating the warning is to do a clean shutdown of the derby database before exiting the jvm which will remove the lck files, but it is hard to know if the user is getting actual dual boot protection under these circumstances.