On a historical note, WmDB was the original and only way that was available to interact with a database. Back when webMethods was a separate company and Integration Server was named B2B Server. When wM bought Active Software (the source of Broker and various adapters) the JDBC adapter was introduced. At the time, wM announced that WmDB was deprecated and would eventually be removed. When that time came, many, many companies objected due to wide and entrenched use of WmDB. So it has been kept.
The guideline these days is anything new should use the JDBC adapter, as @Holger_von_Thomsen suggests. And use of WmDB retired when convenient.
Of course if anyone has alternate info/guideline, please share!
#webMethods#Adapters-and-E-Standards#Integration-Server-and-ESB