disconnect closes a connection to a database specified by database. If successful, success is
t and if only one other connection exists, *default-database* is reset.
The default value for database is *default-database*. If database is a database object, then it is used directly. Otherwise, the list of connected databases is searched to find one with database as its connection specifications (see connect). If no such database is found, then if error and database are both non-nil an error is signaled, otherwise
LispWorks User Guide and Reference Manual - 13 Feb 2015