Exchange Differential Backup Failures after Full Backup Failure

[sbbotto]

Hi,



We have TDP for Exchange v2.2 and backup several Exchange 5.5 servers. Each night a Differential backup is run then a Full backup immediately afterward. If the Full backup fails part way through one night (communication problems or otherwise) the following nights Differential backup will fail with: Unable to perform an incremental backup because a required Microsoft Exchange database log file could not be found.

I realize that if a Full backup is successful it clears out the log files upon completion, but it looks like from what I'm seeing even if the Full backup fails it removes log files that in turn causes the next Differential backup to fail.



Does anyone know if this is true? If so, why are the log files being removed before the Full backup is determined to be "successful".



Scott.

 

[pchapus]

Yes i think it is true! :-o

I am very interested by some clarifications about that "delete" choice or by some news from development.

 

[eavesrb]

The problem you described below sounds allot like the one I am having with an incremental backup failing due to a database log file could not be found. Did you ever get any help with your problem? I just signed up and am not sure how to look for responses.



Thanks,

Richard

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class="pn-sub">Quote:</font><HR></TD></TR><TR><TD><FONT class="pn-sub"><BLOCKQUOTE>Hi,



We have TDP for Exchange v2.2 and backup several Exchange 5.5 servers. Each night a Differential backup is run then a Full backup immediately afterward. If the Full backup fails part way through one night (communication problems or otherwise) the following nights Differential backup will fail with: Unable to perform an incremental backup because a required Microsoft Exchange database log file could not be found.

I realize that if a Full backup is successful it clears out the log files upon completion, but it looks like from what I'm seeing even if the Full backup fails it removes log files that in turn causes the next Differential backup to fail.



Does anyone know if this is true? If so, why are the log files being removed before the Full backup is determined to be "successful".



Scott. </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>

 

[sbbotto]

It appears this is a known problem with Exchange 5.5 and TDP for Exchange.



Solution

There is a registry entry that the Exchange Server 5.5 uses which lists the

last log backed up.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Exchange\BackupInformation\Exchange

MDB Database]

"Last Backup Log"=dword:0000cc7d



(where cc7d is the next to the earliest log file)



The process for the Exchange Server is that the registry entry gets set to

zero when a full backup is started, it then gets reset to the 'correct'

value at some later time during the full backup. If the backup is

terminated, using a tcpip error or even a user cancel, the registry entry

never gets reset and remains at zero. Once set to zero, the next

incremental fails with "Unable to perform incr...because a required...log

file could not be found."



Note that it is Exchange who is setting this log value during the backup

process. This value is most likely being reset to ensure that the correct

log information is included in the full backup. The real problem is the

message that is received from the incremental does not indicate that the

full backup failed. Microsoft is aware of this issue, but since the

Exchange 2000 works differently, it is anticipated that they plan to focus

on this newer product functionality (Exchange 2000 does not encounter this

problem.)



If these messages are received, perform a full backup and possibly

investigate what caused the prior full back to fail.