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