I am trying to backup a Sql Server database via Perl DBI. Calling "backup database" via do() runs but usually does not produce a backup. Calling do() creates a backup when ODBC tracing is enabled. Calling prepare() and execute() fails.

I am using ActiveState Perl on Windows 7 Professional and Sql Server 2008 R2. Here is a link to download source code and various logs http://www.fileswap.com/dl/4VnYbCdk6R/ToZip.zip.html (Click on slow download)

Here is the summary of logs

BothTraces made 3 backups but program aborted
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 09:39 perlEasy.bak
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 09:39 perlHard.bak
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 09:38 queryOS.bak

NoTracing made 1 backup, program aborted
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 10:15 queryOS.bak

DbiTrace made 1 backup, program aborted
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 10:19 queryOS.bak

OdbcTrace made 3 backup but program aborted
-rwx------+ 1 SYSTEM SYSTEM 159744 Jan 16 10:21 perlEasy.bak
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 10:21 perlHard.bak
-rwx------+ 1 SYSTEM SYSTEM 160256 Jan 16 10:21 queryOS.bak

Here's my program:

#!perl -w
#try to use DBI for SQL Server backup 

#connect to database server 
   use v5.14;        #enable modern Perl 
   use DBI;          #database interface
   my $dbHandle = DBI->connect("dbi:ODBC:Driver={SQL Server};Server=DavidZ") or die;   #dbi prints a detailed error message 
   $dbHandle->{RaiseError} = 1;    #enable failure on DBI problems; obviates the need for "or die" with every DBI call
   $dbHandle->{PrintError} = 0;    #don't duplicate error messages 

#enable debugging 
   $dbHandle->trace(1); 
   $dbHandle->{odbc_trace} = 1;                                  #not helpful 
   $dbHandle->{odbc_trace_file} = 'C:\David\dump\tracer.file';   #not helpful 

#run a SQL command to verify connection, write a note to ERRORLOG  
   $dbHandle->do ('use master');
   $dbHandle->do ("raiserror ('New run of backup.pl', 0, 0) with log"); 
   say 'Verified database connection';

#backup commands 
   my $perlEasy = "backup database dz to disk='C:\\David\\dump\\perlEasy.bak'";
   my $perlHard = "backup database dz to disk='C:\\David\\dump\\perlHard.bak'";
   my $queryOS  = "backup database dz to disk='C:\\David\\dump\\queryOS.bak'";

#make a backup via sqlcmd.  this works 
   my $sysCmd = "sqlcmd -Q \"$queryOS\" "; 
   system ($sysCmd) == 0
      or die "The following system command failed:  $sysCmd \n"; 
   say 'Created backup via sqlcmd';

#try to make a backup via DBI 
   $dbHandle->do ($perlEasy);   #runs silently but does not produce a backup file 
   say 'Created backup the easy way';

#more complicated DBI method 
   my $stHandle = $dbHandle->prepare($perlHard);
   $stHandle->execute();     #statement starts a backup then fails, no furter code is executed 

   do 
   {
     #print dbi results 
     say "DBI reports $DBI::errstr"; 

     while (my @row = $stHandle->fetchrow_array())   #recommended by someone, but makes no sense for a backup 
        { say "Returned values: @row" }              #recommended by someone, but makes no sense for a backup 
   } while ($stHandle->{odbc_more_results});

   say 'Created backup the hard way'; 

#program completion
   say 'Program completed successfully';
   exit 0;