sequence value of the record just inserted / DBI

I hope it is OK to ask the question here.

Perl's DBI has the following function.

$rv = $dbh->last_insert_id($catalog, $schema, $table, $field);
"Returns a value 'identifying' the row just inserted, if possible."

I wonder what this $catalog is in this context. It's supposed to be
metadata, and CREATE USER has CATALOG|NOCATALOG option, but what would be
$catalog value for a user table in this context?

Thanks in advance.

Ben Kim