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Re: Challenging performance demand
Posted by: Allen Arakaki
Date: July 13, 2005 02:09PM

You could be bounded by something else (besides the DB tuneable parameters):
Disk, CPU, Memory, Network, etc.

I'm sure you've looked at disk, cpu and memory. How is your app (or test harness) connected to the DB? Is it using a TCP connection or via localhost (UNiX sockets). The IPC mechanism is another good place to look for bottlenecks. The speed of the transport is limited by the number of connections, time of building up and tearing down connections, bandwidth, etc. Even UNIX style sockets may use an underlying IPC mechanism such as memory mapped files, etc. Windows has a bunch of IPC mechanisms. The point is you may have reached the physical limitations of bandwidth (10Mbps for ethernet - more like 70% of that) or number of open sockets (file handles), etc.

For example (bandwidth est.):

10Mbps * byte/10 bits (8 data, 1 parity, 1 cntl) = 1MB/sec * 1024K/M = 1024Kbytes bandwidth - ethernet effective bandwidth (because of collissions etc.) is only about 716Kbytes/sec.

By the looks of your tables, you're moving about 60bytes of data * 4000 tps = 240K bytes/sec + overhead (depends on your connector - SQL passes a bunch of meta data) -- maybe not unreasonable to double or triple the amount of data passed. So you may have already reached your theoretical max moving 480-720Kbytes of data/sec.

If you are using fastethernet (100Mbps), then this is not a problem. If you're using UNIX sockets (local machine IPC mechanism), then you're probably bounded by memory/cpu.

Run netstat (UNIX) and see how many open connections you have. I believe on UNIX, each connection is a filehandle - so check the max number of file handles that can be opened, etc. You can remedy these types of issues by using a DB connection pool.

Anyway you get the idea ...

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