Recycle in a DB2 database means that the database has to deactivated and reactivated. You need two thing for that:
You need to be sure that the database does not continue activated after the last connection is finished. You will execute a "db2 deactivate db xxx" in order to assure that the database will be down after the last connection.
There are not any user connected to the database. You check that with "db2 list applications" and the command should answer that there are not active connections. If there are, and you do not know how to stop naturally, you could a "db2 'force application (xx)'" where xx is the application handle (id) of the list, or you could do a "db2 force application all" and then all connections will be killed.
Recycle for an instance is similar, you need to do a db2stop or db2stop force, and then db2start.
When doing an instance recycle, you will turn off all the databases under that instance.