The goal is execute EBS snapshots of slave data (or data from a slave pair in a replica-pair setup), while read-only clients are connected.

The command "closeAllDatabases" only works on masters.
The only way I found to stop a replication is to send the command "replacepeer" to a replica pair master. It's not really what we would need here, as the "mongod" process of the master has to be restarted to accept a new pair; and the command is sent to the master, not the slave.