Certified Message Delivery

Certified message delivery introduces additional complexity. The performance assessment tool can help you measure its effects on application performance.

When the -cm parameter is present, rvperfm sends messages using Rendezvous certified delivery features. Before each run, it clears its ledger (whether file-based or process-based), and sends a test message to provoke -cm receivers to register for certified delivery. After the registration period, it sends the run of messages.

Number of Certified Receivers

When a certified sender process is operating near maximum capacity (either the capacity of its host computer, or the network capacity), then the number of certified receivers can dramatically affect the timing results.

Throughput of certified messages decreases as the number of registered receivers increases. This decrease is a direct result of confirmation messages flowing back from certified receivers to the sender. You can use the performance tool to measure the network capacity for certified messages with varying numbers of registered receivers.

Ledger

Certified delivery depends on a ledger to track messages and confirmations. Two types of ledger are available; each has a different effect on performance:

•

A file-based ledger with asynchronous I/O offers persistence at the cost of disk operations. With asynchronous file I/O, some information could be lost in the event of sudden termination.

•

A file-based ledger with synchronous I/O offers greater certainty at the cost of additional speed because the disk write operations block. Synchronous file I/O dramatically reduces the probability of lost information in the event of sudden termination.

You can use the performance tool to compare the effect of these options on certified message throughput.