In weblogic pre-12c, Transaction logs were file-based only. In weblogic 12c this has been enhanced with the possibility to store TLogs in a database. Here are the guidelines to achieve this.
First, create a JDBC data source. This can be any type (generic, multi data source or gridlink data source), the only constraint being the it must neither be XA nor support Global Transactions.
Second, go to your server > Configuration > Services tab.
There's a new section here Transaction Log Store.
Switch the type to JDBC and specify your data source which should be in the drop-down list.
You can leave the prefix as-is.
Restart the server and go to your database, you'll see a newly created table TLOG_ADMINSERVER_WLSTORE which has this structure.