The most common reason for an Engine not connecting is either an incorrect parm value in the connection url cdc://[<host_name_or_address>[:<port_number>]]/<agent_name>/<engine_name>or the Engine's public key missing in the Capture Controller's authorized key list.
A more subtle cause can be the re-creation of a publisher configuration .cab file. While not a frequent occurrence it is often the easiest way to add a new target Engine subscription when a large number of source files are involved. The GEN Recovery JCL on the ISPF panel creates a job that can be easily edited to add all the captured databases to both the existing and additional target Engine subscriptions.
SQDF801I Configuration name : kfilepub1.cab
SQDF802I Configuration key : cab_C69D5E516724D2EA
SQDF832I Store File Type : FILE
SQDF836I Filename : /opt/app/sqdata/kfilepub1/data/cab_C69D5E516724D2EA.1They are something like a socket the sqdaemon keeps in memory until recycled. That can be accomplished by either using the ISPF panel, the sqdmon reload command or by terminating and restarting the SQDAEMON process.
Other than that, the only time the sqdaemon needs to be recycled would be if any of the references in the sqdagents.cfg file were modified. Simply adding a new File or target Engine subscription to the publisher .cab would not matter after the change is applied and capture restarted.