SLIME is able to connect to multiple Lisp processes at the same time. The M-x slime command, when invoked with a prefix argument, will offer to create an additional Lisp process if one is already running. This is often convenient, but it requires some understanding to make sure that your SLIME commands execute in the Lisp that you expect them to.
Some buffers are tied to specific Lisp processes. Each Lisp connection has its own REPL buffer, and all expressions entered or SLIME commands invoked in that buffer are sent to the associated connection. Other buffers created by SLIME are similarly tied to the connections they originate from, including SLDB buffers, apropos result listings, and so on. These buffers are the result of some interaction with a Lisp process, so commands in them always go back to that same process.
Commands executed in other places, such as
buffers, always use the “default” connection. Usually this is the
most recently established connection, but this can be reassigned via
the “connection list” buffer:
The buffer displayed by
slime-list-connections gives a one-line
summary of each connection. The summary shows the connection's serial
number, the name of the Lisp implementation, and other details of the
Lisp process. The current “default” connection is indicated with an
The commands available in the connection-list buffer are: