Last time I checked the database handle does not dictate read/write/update/delete access to the database.

The handle results from connecting as a user, so it definitely does. That said, I don't see how this relates.

The code shown has a different function for different operations like update, insert, etc. Each function creates another database handle inside of the function rather than accepting the handle as an argument.

Celebrate Intellectual Diversity

Thank you, I finally found the culprit, it is really DBI (mysql).

This workaround made my program working:

The beginning of my subroutine:

sub write_status($$$$) {
  my $host = $_[0];
  my $app = $_[1];
  my $status = $_[2];
  my $version = $_[3];
  my $result = $dbh->begin_work();
  if (! defined $result) { $result = -1; }
  if ($result < 0) {
    print STDERR "\n" . $0 . ": CHYBA: " . $dbh->errstr . "\n";
    return ISHN_ERR_INTERNAL;
  }
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  my $statement = q{UPDATE results
                    SET status = ?, verze = 'N/A'
                    WHERE host = ? AND app = ?;};
  $result = $dbh->do($statement, undef, $status, $host, $app);
  if (! defined $result) { $result = -1; }
  if ($result <= 0) {
    print STDERR "\n" . $0 . ": CHYBA: " . $dbh->errstr . "\n";
    $dbh->rollback();
    return ISHN_ERR_INTERNAL;
  }
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  $statement = q{UPDATE results
                 SET status = ?, verze = ?
                 WHERE host = ? AND app = ?;};
  $result = $dbh->do($statement, undef, $status, $version, $host, $app
+);
  if (! defined $result) { $result = -1; }
  if ($result <= 0) {
    print STDERR "\n" . $0 . ": CHYBA: " . $dbh->errstr . "\n";
    $dbh->rollback();
    return ISHN_ERR_INTERNAL;
  }
  $statement = q{INSERT INTO history
                 (host, app, status, verze)
                 VALUES (?, ?, ?, ?);};
  $result = $dbh->do($statement, undef, $host, $app, $status, $version
+);
  if (! defined $result) { $result = -1; }
  if ($result <= 0) {
    print STDERR "\n" . $0 . ": CHYBA: " . $dbh->errstr . "\n";
    $dbh->rollback();
    return ISHN_ERR_INTERNAL;
  }
  $result = $dbh->commit();
  if (! defined $result) { $result = -1; }
  if ($result < 0) {
    print STDERR "\n" . $0 . ": CHYBA: " . $dbh->errstr . "\n";
    $dbh->rollback();
    return ISHN_ERR_INTERNAL;
  } else { return ISHN_OK; }
}
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