Maximum retrieval

The maximum value retrieval mode returns the maximum value from the actual data values within a retrieval cycle. If there are no actual data points stored on the historian for a given cycle, nothing is returned. NULL is returned if the cycle contains one or more NULL values.

As in cyclic retrieval, the number of cycles is based on the specified resolution or cycle count. However, maximum retrieval is not a true cyclic mode. Apart from the initial value, all points returned are delta points.

Maximum retrieval only works with analog tags. For all other tags, normal delta results are returned.

All returned values are in chronological order. If multiple points are to be returned for a particular timestamp, they are returned in the order in which the tags were specified in the query. If the maximum value occurs several times in a cycle, the maximum value with the earliest timestamp is returned.

The maximum retrieval mode must use the "<=" operator for the ending date/time.

Using the maximum retrieval mode with a cycle count of 1 returns the same results as the SQL Server MAX aggregate; however, the data is returned much faster.