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From Øystein Grøvlen (JIRA) <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-298) rollforward will not work correctly if the system happens to crash immediately after rollforward backup.
Date Thu, 22 Dec 2005 11:12:31 GMT
    [ http://issues.apache.org/jira/browse/DERBY-298?page=comments#action_12361100 ] 

Øystein Grøvlen commented on DERBY-298:
---------------------------------------

The recently attached patch (derby-298a.diff) addresses Suresh's
review comments.  The only major change from the previous patch is in
java/engine/org/apache/derby/impl/store/raw/log/Scan.java. The changes
to this file compared to the current head of trunk are:
 
   - When a new log file is entered, check that the header of this
     file refers to the end of the last log record of the previous log
     file.  If not, stop the scan.
   - If the header was consistent, update knowGoodLogEnd to the first
     possible LogInstant of this file (end of header).
   - close() no longer reset knownGoodLogEnd since it is needed by
     FileLogger after the scan is closed.
   - Changed comment of getLogRecordEnd() to reflect that it can be
     used after the scan is closed, and that it at that time may
     return the start of an empty log file.
   - Removed comment about not starting to write to the new empty log
     file, since that is not true anymore.

In addition, the property files for the tests have been updated so
they are run without the security manager.

derbyall has been run with no new failures.


> rollforward will not work correctly  if the system happens to crash immediately after
rollforward backup.
> ---------------------------------------------------------------------------------------------------------
>
>          Key: DERBY-298
>          URL: http://issues.apache.org/jira/browse/DERBY-298
>      Project: Derby
>         Type: Bug
>   Components: Store
>     Versions: 10.0.2.1
>     Reporter: Suresh Thalamati
>     Assignee: Øystein Grøvlen
>     Priority: Minor
>  Attachments: derby-298.diff, derby-298a.diff
>
> If the system crashes after a rollforward backup; last log file 
> is empty(say log2.dat). On next crash-recovery system ignores the  empty log 
> file and starts writing to the previous log(say log1.dat),  
> even thought there was successfule log file switch  before the crash.
> The reason I belive it is done this way to avoid special 
> handling of crashes  during the log switch process. 
> Problem is  on rollfroward restore from a backup log1.dat will get overwritten 
> from the copy in the backup, so any transaction that got added to log1.dat
> after the backup was taken will be lost. 
>  
> One possible solution that comes to my mind to solve this problem is 
>  1) check if an  empty a log file exist after a redo crash-recovery , if 
>      the log archive mode is enabled.
>  2) If it exists , delete and do log file switch again 
>  
> Repro:
> connect 'jdbc:derby:wombat;create=true';
> create table t1(a int ) ;
> insert into t1 values(1) ;
> insert into t1 values(2) ;
> call SYSCS_UTIL.SYSCS_BACKUP_DATABASE_AND_ENABLE_LOG_ARCHIVE_MODE(
>     'extinout/mybackup', 0);
> --crash (NO LOG RECORDS WENT IN AFTER THE BACKUP).
> connect 'jdbc:derby:wombat';
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> insert into t1 select a*2 from t1 ;
> select count(*) from t1 ;
> --exit from jvm and restore from backup
> connect
> 'jdbc:derby:wombat;rollForwardRecoveryFrom=extinout/mybackup/wombat';
> select count(*) from t1 ;  -- THIS WILL GIVE INCORRECT VALUES

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