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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] Created: (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.
Date Wed, 24 Nov 2010 23:41:14 GMT
zero byte dbex.lck file can cause dual boot warning saying Severe and non-recoverable corruption
can  result and may have already occurred.
-------------------------------------------------------------------------------------------------------------------------------------------

                 Key: DERBY-4917
                 URL: https://issues.apache.org/jira/browse/DERBY-4917
             Project: Derby
          Issue Type: Bug
          Components: Store
    Affects Versions: 10.1.2.1
         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)
            Reporter: Kathey Marsden


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.
 


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