diff --git a/lib/Simba/CA.pm b/lib/Simba/CA.pm
index 16f0daf..2ad0c9a 100644
--- a/lib/Simba/CA.pm
+++ b/lib/Simba/CA.pm
@@ -239,6 +239,7 @@ sub release_fileset {
 
     $self->log(3, "releasing fileset $target->{id}");
     $self->{dbh}->do(q{update filesets set pid=null where id=? and pid=?}, {}, $target->{id}, $$);
+    $self->{dbh}->commit();
 }
 
 
@@ -569,6 +570,7 @@ sub new_session {
 sub close_session {
     my ($self) = @_;
     $self->{dbh}->do("update sessions set end_date=? where id=?", {}, time(), $self->{session_id});
+    $self->{dbh}->commit();
     $self->close_file_connection;
     delete $self->{target};
 }
@@ -827,6 +829,7 @@ sub export {
     my ($self) = @_;
     my $dbh = $self->{dbh};
     my $exportdir = $self->basedir . "/export";
+    mkdir($exportdir);
 
     my $sessions = $dbh->selectcol_arrayref("select id from sessions order by id");
     for my $session_id (@$sessions) {
@@ -848,14 +851,14 @@ sub export {
                      and files.fileset=filesets.id
                 });
         $sth->execute;
-        open my $fh, '>', "$exportdir/$session_id.tsv.$$";
+        open my $fh, '>', "$exportdir/$session_id.tsv.$$" or die "cannot create $exportdir/$session_id.tsv.$$: $!";
         print $fh join("\t", @{$sth->{NAME}}), "\n";
         while (my $r = $sth->fetchrow_arrayref) {
             no warnings 'uninitialized';
-            print $fh join("\t", @$r), "\n";
+            print $fh join("\t", @$r), "\n" or die "cannot write to $exportdir/$session_id.tsv.$$: $!";
         }
         close($fh);
-        rename "$exportdir/$session_id.tsv.$$", "$exportdir/$session_id.tsv";
+        rename "$exportdir/$session_id.tsv.$$", "$exportdir/$session_id.tsv" or die "cannot rename $exportdir/$session_id.tsv.$$ to $exportdir/$session_id.tsv: $!";
         system "/bin/gzip", "$exportdir/$session_id.tsv";
     }