JetGetSystemParameter Function

Article
08/26/2021

Applies to: Windows | Windows Server

JetGetSystemParameter Function

The JetGetSystemParameter function reads the numerous configuration settings of the database engine.

    JET_ERR JET_API JetGetSystemParameter(
      __in          JET_INSTANCE instance,
      __in          JET_SESID sesid,
      __in          unsigned long paramid,
      __in_out_opt  JET_API_PTR* plParam,
      __out_opt     JET_PSTR szParam,
      __in          unsigned long cbMax
    );

Parameters

instance

The instance to use for this call.

For Windows 2000, this parameter is ignored and should always be NULL.

For Windows XP and later releases, this parameter is somewhat overloaded. If the engine is operating in legacy mode (Windows 2000 compatibility mode) where only one instance is supported, this parameter may be NULL or may contain the actual instance returned by JetInit. In either case, all system parameter settings are read from that one instance. If the engine is operating in multi-instance mode, this parameter may be NULL or a pointer to an instance created using JetInit or JetCreateInstance. When this parameter is NULL then the global system parameter setting (or default) is read. When this parameter is an instance then the system parameter setting for that instance is read.

sesid

The session to use for this call.

When specified, the specified instance is ignored and the instance associated with the session will be used.

paramid

The ID of the system parameter that will be read.

See System Parameters for a complete list of system parameters and their properties.

plParam

The output buffer that receives the value of the selected system parameter if that system parameter is of an integer type.

szParam

The output buffer that receives the value of the selected system parameter if that system parameter is of a string type.

cbMax

The maximum size in bytes of the string output buffer.

Return Value

This function returns the JET_ERR datatype with one of the following return codes. For more information about the possible ESE 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_errInitInProgress	It is not possible to complete the operation because the instance associated with the session is being initialized.
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. This can happen for JetGetSystemParameter when: The specified system parameter ID is invalid or unsupported. The specified system parameter requires the integer output buffer to be provided and that output buffer pointer was NULL. The specified system parameter requires a string output buffer to be provided and that output buffer pointer was NULL. Windows Vista: This can only happen on Windows Vista and later releases. The specified system parameter requires a string output buffer to be provided and the size of that output buffer is too small to accept a null terminated string. Windows Vista: This can only happen on Windows Vista and later releases. The specified system parameter cannot be read because it is write-only. The specified system parameter is global only and an attempt was made to read an instance specific value for that system parameter. This can only happen on Windows XP and later releases. The specified system parameter is per-instance only and an attempt was made to read the global value for that system parameter. This can only happen on Windows XP and later releases.
JET_errNotInitialized	It is not possible to complete the operation because the instance associated with the session has not been initialized yet.
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.
JET_errInvalidSesid	The session handle is invalid or refers to a closed session. This error is not returned under all circumstances. Handles are validated on a best effort basis only.
JET_errInvalidInstance	The instance handle is invalid or refers to an instance that has been shutdown. This error is not returned under all circumstances. Handles are validated on a best effort basis only. Windows Vista: This error will only be returned by Windows Vista and later releases.
JET_wrnBufferTruncated	The operation completed successfully, but the output buffer was too small to receive the entire system parameter setting. The output buffer has been filled with as much of the system parameter setting as would fit. If the output buffer is at least one character in length then the string in that output buffer will be null terminated. Note This error is not returned by all releases. Please see the Remarks section for more information.
JET_errBufferTooSmall	The operation failed because the output buffer was too small to receive the entire system parameter setting. Note This error is not returned in some cases to preserve application compatibility. Please see the Remarks section for more information. Windows Vista: This error will only be returned by Windows Vista and later releases.

On success, the output buffer appropriate for the requested system parameter will be set to the value of that system parameter.

On failure, the state of the output buffers will be undefined.

Remarks

There is an important problem in this API that is present in all releases. If a system parameter with a string value is requested and the output buffer is too small to receive the entire system parameter setting, JET_wrnBufferTruncated will NOT be returned. JET_errSuccess is returned instead. If the length of the returned string is equal to the size of the output buffer less the NULL terminator, the caller should react as if JET_wrnBufferTruncated were returned. If a zero-sized string output buffer is specified, the caller should react as if JET_errInvalidParameter were returned.

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 JetGetSystemParameterW (Unicode) and JetGetSystemParameterA (ANSI).

JetGetSystemParameter Function