LockServiceDatabase

The LockServiceDatabase function locks a specified database.

SC_LOCK LockServiceDatabase(

SC_HANDLE hSCManager	// handle of service control manager database
);

Parameters

hSCManager

Identifies the service control manager database. The OpenSCManager function returns this handle, which must have SC_MANAGER_LOCK access.

Return Values

If the function succeeds, the return value is a lock to the specified service control manager database.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Errors

The following error code may be set by the service control manager. Other error codes may be set by registry functions that are called by the service control manager.

Value	Meaning
ERROR_ACCESS_DENIED	The specified handle was not opened with SC_MANAGER_LOCK access.
ERROR_INVALID_HANDLE	The specified handle is invalid.
ERROR_SERVICE_DATABASE_LOCKED	The database is locked.

Remarks

The LockServiceDatabase function tries to acquire a lock on the specified database. Only one process at a time can have a lock on a database.

A lock is a protocol used by setup and configuration programs and the service control manager to serialize access to the service tree in the registry. The only time the service control manager acquires a lock is when it is starting a service. Setup and configuration programs are expected to acquire a lock before using the ChangeServiceConfig or SetServiceObjectSecurity function to reconfigure a service. They should also acquire a lock before using the registry functions to reconfigure a service. The lock prevents the service control manager from starting a service while it is being reconfigured.

A call to the StartService function to start a service in a locked database fails. All other service control manager functions are not affected by a lock.

The lock is held until the SC_LOCK handle is specified in a subsequent call to the UnlockServiceDatabase function. If a process that is holding a lock terminates, the service control manager automatically cleans up and releases the lock.

See Also

ChangeServiceConfig, OpenSCManager, QueryServiceLockStatus, SetServiceObjectSecurity, StartService, UnlockServiceDatabase

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