Client manager

The client manager is the part that handles the communications with the client. The client can be a (web) server or an end-user/end-application. The client manager provides different ways to access the database through a set of well-known APIs: JDBC, ODBC, OLE-DB …

It can also provide proprietary database access APIs.

When you connect to a database:

• The manager first checks your authentication (your login and password) and then checks if you have the authorizations to use the database. These access rights are set by your DBA.
• Then, it checks if there is a process (or a thread) available to manage your query.
• It also checks if the database if not under heavy load.
• It can wait a moment to get the required resources. If this wait reaches a timeout, it closes the connection and gives a readable error message.
• Then it sends your query to the query manager and your query is processed
• Since the query processing is not an “all or nothing” thing, as soon as it gets data from the query manager, it stores the partial results in a buffer and start sending them to you.
• In case of problem, it stops the connection, gives you a readable explanation and releases the resources.