Release 4.3: DB_ENV->set_verbose

The 4.3 release removes support for the DB_ENV->set_verbose() method flag DB_VERB_CHKPOINT. Application writers should simply remove any use of this flag from their applications.

The 4.3 release redirects output configured by the DB_ENV->set_verbose() method from the error output channels (see the DB_ENV->set_errfile() and DB_ENV->set_errcall() methods for more information) to the new DB_ENV->set_msgcall() and DB_ENV->set_msgfile() message output channels. This change means the error output channels are now only used for errors, and not for debugging and performance tuning messages as well as errors. Application writers using DB_ENV->set_verbose() should confirm that output is handled appropriately.