Public Overloads Function ReadMaxAge( _
   ByVal srvHnd() As Integer, _
   ByVal maxAge() As Integer, _
   ByVal transactionID As Integer, _
   ByRef cancelID As Integer, _
   ByRef errors As Integer() _
) As Integer

public int ReadMaxAge( 
   int[] srvHnd,
   int[] maxAge,
   int transactionID,
   out int cancelID,
   out int[] errors
)

Parameters

srvHnd

Array of server item handles of the items to be read

maxAge

An array of “staleness” for each item, requested in milliseconds. The server will calculate, for each requested item, the number of milliseconds between “now” and the timestamp on each item. For each item that has not been updated within the last MaxAge milliseconds, the item must be obtained from the underlying device. Or if the item is not available from the cache, it will also need to be obtained from the underlying device. A max age of 0 is equivalent to OPC_DS_DEVICE and a max age of 0xFFFFFFFF is equivalent to OPC_DS_CACHE. Without existence of a cache the server will always read from device. In this case MaxAge is not relevant. Clients should not expect that a cache exists, if they have not activated both the item and the containing group. Some servers maintain a global cache for all clients. If the needed item is in this global cache, it is expected that the server makes use of it to check the MaxAge value. Servers should not automatically create or change the caching of an item based on a Read call with MaxAge. (Note: Since this is a DWORD of milliseconds, the largest MaxAge value would be approximately is 49.7 days).

transactionID

The Client generated transaction ID. This is included in the 'completion' information provided to the OnReadComplete.

cancelID

Place to return a Server generated ID to be used in case the operation needs to be canceled.

errors

Return Value

Target Platforms: Windows 7/8/10, Windows Server 2003/2008/2012/2016, .NET 4.x

See Also