This function changes the priority of a queued transaction and, if necessary, moves the transaction to a new location in its queue.

In addition to id and response-format, this function requires the priority parameter, which takes an integer value from 1 to 5 inclusive. There is no default. If its value is specified as less than 1, it is adjusted to 1. If its value is specified as greater than 5, it is adjusted to 5.

If this function raises a transaction's priority, the transaction is moved so that it becomes the last transaction of the set of transactions with its new priority. If this function lowers a transaction's priority, the transaction is moved so that it becomes the first transaction of the set of transactions with its new priority. (The principle is to move a transaction the minimum number of places necessary to keep the queue sorted in priority order.)

If this request specifies an immediate request, a queued transaction that has finished, or if the id parameter does not identify an active transaction, this function will return an error.