I don't know if the Sybase driver supports it, but flaky servers suggest the DBI $dbh->ping method. You can open a handle to each server, say $dbx and $dby, and use the trinary op to select my $sth = ($dbx->ping ? $dbx : $dby)->prepare('select 1+1'); and so on. That will get awkward fast.

Another approach is to first try to connect to x. If that fails, connect to y. That isn't what you want for a long running process, but for a one-shot script it is probably ok (you wanted tolerant, not immune, right?)

my $dbh = connect($x_string, $x_nam, $x_pass)
        || connect($y_string, $y_nam, $y_pass)
        or die 'No db!';
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package DBI_Wrapper;

sub new
{
    my $class = shift;

    my $self = bless {
        dbh => [],
        active => 0,
    }, $class;
}

sub add_dbhs
{
    my $self = shift;

    push @{$self->{dbh}}, @_;
}

sub AUTOLOAD
{
    my $meth = our $AUTOLOAD;
    (my $func = $meth) =~ s/.*:://;

    my $self = shift;

    my $start = $self->{active};
    my $dbh;
    while (1)
    {
        $dbh = $self->{dbh}->[$self->{active}];
        eval { $dbh->ping };
        last unless $@;

        $self->{active}++;
        $self->{active} %= @{$self->{dbh}};
        die "No valid DBH found\n" if $self->{active} == $start;
    }

    return $dbh->$meth( @_ );
}
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Or, something like that. :-)

You'll need to spend some time to evaluate each one to see if it addresses your purposes, but depending on your requirements, this may be much easier than writing your own from scratch.

Michael