Client Connection

For a client application, a connection is the mechanism that the application uses to request a synchronization with the database server for the purpose of exchanging data. A client application (such as an ESQL/C or client LIBMI application) takes the following steps to request a connection:

1. Initializes the connection

   A client LIBMI application can set connection, database, and session parameters to determine attributes of the connection.

   For more information, see Initializing a Client Connection.

2. Establishes the connection

   An ESQL/C client application uses SQL statements (such as CONNECT or DATABASE) to establish a connection. A client LIBMI application uses the DataBlade API to establish a connection in either of the following ways:

   • Uses the mi_open( ) function
   • Uses the mi_server_connect( ) function

   For more information, see Establishing a Client Connection.

When a client application connects to the database server, the database server performs the following tasks:

• Creates a session structure, called a session control block, to hold information about the connection and the user
• Creates a thread structure, called a thread-control block (TCB), to hold information about the current state of the thread
• Determines the server-processing locale, the locale to use for SQL statements during the session
• Initializes a primary thread, called the session thread (or sqlexec thread), to handle client-application requests

When the client application successfully establishes a connection, it begins a session. Only a client application can begin a session. The session context consists of data structures and state information that are associated with a specific session, such as cursors, save sets, and user data.