RE: dedicated sessions

[Ferenc Mantfeld]

My experience is that MTS is fine until you get into the 400 - 500 concurrent user range, and then it goes to hell in a hand basket. The CPU usage itself will not be very high, but that is because MTS under heavy load precludes the DB from doing any useful work, as it spends a lot of its resources trying to manage shared server and dispatcher processes and steps over itself trying to do what the OS was designed to do for heavy user loads, i.e. CPU time slicing in a bastardized form. MTS seems to give better performance under weenie-doze, but look at what you're dealing with, a wanna-be OS that could probably use any assistance it can get from the application (oracle rdbms).   I am of the opinion that is is far easier to purchase more memory to run the dedicated sessions than put yourself through the masochistic daily rituals of trying to tune and stay on top of what MTS is doing, at least in a high user load environment.   I have only seen one of our customers use MTS where they had > 500 concurrent users, and the reason I know this is because I was called out to do a performance tuning gig on their system. The minute they turned off MTS, things started to go much smoother. Then again, they were using 10 TCP/IP dispatcher processes to run 2,300 concurrent users. Their DBA was still in the stage of being a DBB, and thus still believed everything he read in the Oracle manuals, or worse still, the press releases.   Perhaps other listers have different experiences with MTS. If so, please share your golden nuggets of wisdom. Up to now, I am still not impressed with the product to handle high user volumes, but am always open to someone showing me where I am not looking. Regards: Ferenc Mantfeld Senior Performance Engineer Siebel Performance Engineering Melbourne, 3000, VIC, Australia Only Robinson Crusoe had all his work done by Friday -----Original Message----- From: Alexandre Gorbatchev [mailto:[EMAIL PROTECTED]] Sent: Tuesday, 18 June 2002 4:08 AM To: Multiple recipients of list ORACLE-L Subject: Re: dedicated sessions Hi,   you have lower memory requirement with shared servers. It may also improve performance in case dedicated connections take so much memory that it goes to use a swap. Guidelines - use dedicated connections if you have enough memory to hande them or if connections are always active. If each connection makes few requests to the database, you may not notice any noticeable difference in performance. The lost of performance (as far as i know; correct me if i'm wrong) happens mostly when shared connections wait for busy server process to become free. Another lost of performance with shared servers comes from dispatchers, but it's very light overhead I believe.   -- HTH, Alexandre   ----- Original Message ----- From: Yechiel Adar To: Multiple recipients of list ORACLE-L Sent: Tuesday, June 18, 2002 11:53 AM Subject: Re: dedicated sessions Hello Bp   The topic was discussed on the list some time ago. The trade off seems to be memory vs. CPU. If I recall correctly MTS use more resources and dedicated connection use about 3MB for each connection on NT.   Yechiel Adar Mehish ----- Original Message ----- From: BigP To: Multiple recipients of list ORACLE-L Sent: Thursday, June 13, 2002 12:49 AM Subject: dedicated sessions Hi List , Is there any way I can make shared connectiuon explicitely . When I am looking at v$session I am finding tons of JDBC connection which are dedicated . Can I expect some performance gain or low resource requirement out of this if I make these dedicated connections to shared . Thanks , Bp