Each database has a single server process. The server process is the core component of the CUBRID database server, and handles a user's requests by directly accessing database and log files. The client process connects to the server process via TCP/IP communication. Each server process creates threads to handle requests by multiple client processes. System parameters can be configured for each database, that is, for each server process. The server process can connect to as many client processes as specified by the max_clients parameter value.
The master process is a broker process that allows the client process to connect to and communicate with the server process. One master process runs for each host. (To be exact, one master process exists for each connection port number specified in the cubrid.conf system parameter file.) While the master process listens on the TCP/IP port specified, the client process connects to the master process through that port. The master process changes a socket to server port so that the server process can handle connection.
All CUBRID programs except the server process have two modes: client/server mode and standalone mode.
For example, database creation and restore utilities run in standalone mode so they can use the database exclusively by denying the access by multiple users. Another example is that the CSQL Interpreter can either connect to the server process in client/server mode or execute SQL statements by accessing the database in standalone mode. Note that one database cannot be accessed simultaneously by server processes and standalone programs.