The MERGE option controls the number of rows per request for the form that takes a dataset (MERGE does not apply to the forms of SOAPCALL that take a single row as input). If MERGE(m) is specified, each request contains up to m rows, rather than a single row.

If the concurrency (PARALLEL option setting) is less than or equal to the number of URLs then each URL will normally only see one request at a time (assuming all hosts operate at about the same speed). In that case, you might choose a value of MERGE as high as the host and the network can take: too high a value and a massive request might kill or swamp the service, but too low a value needlessly increases overhead by sending many small requests in place of fewer larger ones. If the concurrency is greater than the number of URLs then each URL will see several requests at a time and these considerations still apply.

Assuming that the host processes a single request serially, there is one additional consideration. You should ensure that the MERGE value is smaller than the number of rows in the dataset so as to ensure that you are making use of the parallelization on the hosts. If the value of MERGE is greater than or equal to the number of input rows, then you send the entire input dataset in one request and the host processes the rows serially.

You should add the MERGE option to the code from the second example to see what effect differing values may have in your environment.