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SQL Anywhere 11.0.0 » SQL Anywhere Server - Programming » SQL Anywhere Data Access APIs » SQL Anywhere web services » Using HTTP sessions


Session semantics

An HTTP request can create an HTTP session context. A session created by the request is always immediately instantiated so that any subsequent HTTP requests requiring that session context is queued by the session.

An HTTP request that begins with no session but has created its session context is the creator of its session. The creator request can change or delete its session context where any change or deletion occurs immediately. An HTTP request that begins within a session context can also change or delete its session. A change made to its session immediately creates a pending session that is fully functional with the exception that another HTTP request cannot take ownership (an incoming request requiring the pending session would instead be queued on the session). To summarize, changing or deleting a session of a creator request modifies the current session context immediately, while a request only changing its session modifies its pending session. When an HTTP request finishes, it checks to see if it has a pending session. If a pending session exists, it deletes its current session and replaces it with the pending session. The database connection cached by the session is effectively moved to the new session context and all state data, such as temporary tables and created variables, are preserved.

In all cases, whenever an HTTP session is deleted, any requests within its queue are released and allowed to execute without a session context. Application code expecting that a request is running within a session context must attempt to acquire a valid session context by calling CONNECTION_PROPERTY('SessionID').


If an HTTP request is canceled either intentionally or because of network failure, an existing pending session is deleted preserving the original session context. A creator HTTP request, whether canceled or having terminated normally, changes session state immediately.