JetBeginSession Function

Article
08/26/2021

Applies to: Windows | Windows Server

JetBeginSession Function

The JetBeginSession function starts a session and initializes and returns an ESE session handle (JET_SESID). Sessions control all access to the database and are used to control the scope of transactions. The session can be used to begin, commit, or abort transactions. The session is also used to attach, create, or open a database. The session is used as the context for all DDL and DML operations. To increase concurrency and parallel access to the database, multiple sessions can be begun.

    JET_ERR JET_API JetBeginSession(
      __in          JET_INSTANCE instance,
      __out         JET_SESID* psesid,
      __in_opt      JET_PCSTR szUserName,
      __in_opt      JET_PCSTR szPassword
    );

Parameters

instance

The database instance to use for this call.

psesid

Pointer to the variable that the session handle initializes on successful return.

szUserName

This parameter is reserved.

szPassword

This parameter is reserved.

Return Value

This function allows for the return of any JET_ERRs that are defined in this API. For more information about Jet errors, see Extensible Storage Engine Errors and Error Handling Parameters.

Return code	Description
JET_errSuccess	The operation completed successfully.
JET_errClientRequestToStopJetService	It is not possible to complete the operation because all activity on the instance associated with the session has ceased as a result of a call to JetStopService.
JET_errInstanceUnavailable	It is not possible to complete the operation because the instance associated with the session has encountered a fatal error that requires that access to all data be revoked to protect the integrity of that data. This error will only be returned by Windows XP and later releases.
JET_errInvalidParameter	One of the parameters provided contained an unexpected value or contained a value that did not make sense when combined with the value of another parameter.
JET_errNotInitialized	It is not possible to complete the operation because the instance associated with the session has not been initialized yet.
JET_errOutOfMemory	The operation failed because memory could not be allocated.
JET_errOutOfSessions	The number of sessions the engine will allow the client to start is limited. This value can be changed using JetSetSystemParameter with the JET_paramMaxSessions constant. The default number of sessions is 16. See System Parameters for details about JET_paramMaxSessions.
JET_errRestoreInProgress	It is not possible to complete the operation because a restore operation is in progress on the instance associated with the session.
JET_errTermInProgress	It is not possible to complete the operation because the instance associated with the session is being shut down.

On success, the session handle is initialized, and may be used for database operations.

On failure, there are no available sessions or a new session was unable to be initialized.

Remarks

Careful attention must be used when using sessions across different threads. A session tracks which thread it was used on during JetBeginTransaction, JetCommitTransaction, or JetRollback, and it will throw an error if used on multiple threads with an open transaction. The JetResetSessionContext, JetSetSessionContext can change this behavior. Since the session is still a serialized context, and multiple database operations cannot be performed on a single session concurrently, only serially. However, you can use multiple sessions to achieve concurrent database access. Sessions can be used inside a transaction across threads by setting and resetting the session contexts.

The session handle should be closed with JetEndSession.

Requirements

Requirement	Value
Client	Requires Windows Vista, Windows XP, or Windows 2000 Professional.
Server	Requires Windows Server 2008, Windows Server 2003, or Windows 2000 Server.
Header	Declared in Esent.h.
Library	Use ESENT.lib.
DLL	Requires ESENT.dll.
Unicode	Implemented as JetBeginSessionW (Unicode) and JetBeginSessionA (ANSI).

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JetBeginSession Function