Increasing Subscriber Message-Transfer Performance

Improve message-transfer performance of the RAPCache and RAPStore subscribers.

RAPCache and RAPStore subscriber performance settings
Parameter	Description
Log Level	Controls the amount of information that is logged during system operation. Logging information is expensive, so adjust this level as low as possible for effective system operation. Set this value to error or warning for optimal performance.
Number of Packet Buffers	Packet buffers are in-memory buffers that the subscriber uses to store arriving packets until they are processed by the subscriber. Specify the number of packet buffers for each data stream channel. Increase this parameter if the message sending rate of the publisher exceeds the message receiving rate of the subscriber. If the subscriber can process data at a rate matching the data sent by the publisher, a value of 20–35 packet buffers per data stream channel allows for small bursts of increased traffic.
Packet Window Size	Subscribers may receive network packets in an order other than the order in which they were sent. If a packet is received out of sequence, the packet window size determines how many additional packets can be received before a resend request is sent for the missing packet. A very small value can result in requesting resends for packets that arrive out of order due to network latencies. A very large value increases the latency that occurs when packets are actually lost over the network. The packet window size is related to the number of packet buffers. The packet window size of a subscriber should be 80–90% of the number of packets cached by the publisher to ensure that the publisher can send missing packets in response to resend requests. Warning! Do not set this parameter to a value that exceeds the number of packet buffers allocated to its publisher; doing so results in data loss when resends are required.
Data Stream Channel List	This parameter lists the data stream channel definitions for the subscriber. The list should match the data stream channel list defined for the publishers to which this subscriber is subscribed. Increase the number of data stream channels if the message sending rate of the publisher exceeds the message receiving rate of the subscriber. However, a very large number of data channels may result in resource contention, which has a negative impact on the overall system performance.