This id generation strategy is specified in the mapping file as

CopyC#

<generator class="hilo">
    <param name="table">table</param>
    <param name="column">id_column</param>
    <param name="max_lo">max_lo_value</param>
    <param name="schema">db_schema</param>
</generator>

The table and column parameters are required, the max_lo and schema are optional.

The hi value MUST be fecthed in a seperate transaction to the ISession transaction so the generator must be able to obtain a new connection and commit it. Hence this implementation may not be used when the user is supplying connections. In that case a SequenceHiLoGenerator would be a better choice (where supported).