/*D
   MPI_T_pvar_start - Start a performance variable

Synopsis:
.vb
int MPI_T_pvar_start(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
.ve

Input Parameters:
+ session - identifier of performance experiment session (handle)
- handle - handle of a performance variable (handle)

Notes:
If the constant MPI_T_PVAR_ALL_HANDLES is passed in handle, the MPI implementation
attempts to start all variables within the session identified by the parameter session for
which handles have been allocated. In this case, the routine returns MPI_SUCCESS if all
variables are started successfully, otherwise MPI_T_ERR_PVAR_NO_STARTSTOP is returned.
Continuous variables and variables that are already started are ignored when
MPI_T_PVAR_ALL_HANDLES is specified.

.N ThreadSafe

.N Errors
.N MPI_SUCCESS
.N MPI_T_ERR_INVALID_HANDLE
.N MPI_T_ERR_INVALID_SESSION
.N MPI_T_ERR_NOT_INITIALIZED
.N MPI_T_ERR_PVAR_NO_STARTSTOP
.N MPI_ERR_OTHER

D*/

