z/OS® Explorer and Developer for z/OS consists of multiple permanently active servers, which can be started tasks or user jobs. These servers provide the requested services themselves or start other servers (as z/OS UNIX threads or user jobs) to provide the service. There is no specific startup order.
The only requirement is that the servers are up and running before the first user tries to connect. The security mechanisms used by z/OS Explorer and Developer for z/OS servers and services rely on the data sets and file systems they reside in being secure. This implies that only trusted system administrators should be able to update the program libraries and configuration files.