JBPM_LOG table column 'exception' is too small, throws RE: ORA-01461: can bind a LONG value only for insert into a LONG column

If an action throws an exception, the stack trace is logged in the JBPM_LOG table.
However, in case of a very long stack trace (longer than 4000 characters), this throws an oracle Exception.
"RE: ORA-01461: can bind a LONG value only for insert into a LONG column"

The bug is difficult to trace, since the exception is only thrown at hibernate session.flush() and not at the actual insert...

Actual exception stacktrace that presented the problem was the exception stacktrace of weblogic, 7200 chars. (the jbpm action was executing business logic running in its own transaction).