Re: A little problem with transfer

On Nov 27, 5:22 pm, "Marcin" <t..._at_spmat0op.pl> wrote:
> Hello
> I got a problem with Oracle (? not sure)
> We use oracle 9 on few systems (solaris, centos, fedora)
> When I am conected to the oracle (aplication or pl/sql) I have transfer
> about 100kb
> When I am conected thru NAT (cisco) or VPN (cisco or openvpn) my transefer
> from oracle is no more then 20 kb :(
> In this same time ftp transfer is about 400kb
>
> I am sure that is not cisco and line is ok (checke on few routers few lines)
>
> Do you have any sugestions?
>
> Marcin

With the inclusion of terms NAT and VPN, I am assuming that you are attempting to compare application database performance with that of an FTP transfer over a high latency (10+ ms ping times) WAN link. To keep the numbers simple, assume that the WAN link has a 100ms ping time - it takes 0.1 seconds to send a packet from the remote client to the server, and for the server to send back a response stating that it received the packet. Even if there was no processing required at either end, if the client only sends one packet at a time to the server (requesting one row at a time, for example), there will be a maximum of ten such communications per second, if the client waits for the previous packet to be returned before requesting the next.

Assume that the client requests data, as suggested by Joel and previously by Sybrand, with an SDU set at 2KB. With a latency of 100ms and a 2KB SDU, you will hit a maximum transfer rate of roughly 20KB, or 160Kb per second. FTP transfers operate differently - the sending server may send 2-15 (or more) of roughly 1500 byte packets before pausing for the client to send an ACK indicating that the previous group of packets were received without error. This greatly increases throughput. Image the performance difference between the two methods if the WAN link is a satellite link with a latency of 1000ms to 2000ms.

With additional details, more help may be possible.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Thu Nov 29 2007 - 06:31:23 CST