Re: NET or CPU VP Class

Sean Kelsey wrote: > Good morning Informixers. > > We have been going through a series of conversations with Informix technical > support and I thought I would like to test all you DBA's out there as to > what the general consensus is regarding the VP class that the soctcp poll > thread should run on. > > We are using IDS 7.30.FC6 on HP-UX 11.x. We were having problems with > earlier releases of the engine ( 7.24.UC7 ) where we were getting Assert > Failures due to the soctcppoll thread crashing. Informix Tech Support told > us that it was a know bug and we should adopt to one of the following:- > > 1. Reduce the number of poll threads that run > 2. Increase the number of users that each poll thread services > 3. change the class of VP from CPU to NET > ( 4. Upgrade, of course ) > > As you can see from the below NETTYPE settings, we opted for a mixture of 1 > & 2 but we are occasionally getting the same assert failure. > > NETTYPE ipcshm,1,50,NET > NETTYPE soctcp,2,300,CPU # This is the new one > # NETTYPE soctcp,3,200,CPU # This was the old setting > NETTYPE sqlmux,,,> How many physicals CPU's does the machine have? How many CPU VP's do you have configured? If a majority of your users are comin in via network, then you're better off using CPU VP's for the socket threads - the CPU VP's spend most of their time on the CPU's, it makes sense to have them handle the connections also to reduce context switching. However, do not have more socket threads than you have CPU VP's - simple math :-) The optimal value for each socket thread is 80-100 users. Tech. support claims that socket threads can service upto 200 users without any performance issues, try it out for yourself. The downside of this approach is if the sessions themselves are CPU bound, then your users will see increased delays at connect time and timeouts in some cases. This happened to me at a 600GB datawarehouse shop with 250 users and all were running complex business objects queries (tons of group-by's, order-by's, and nested subqueries). Good luck, Arun > > So, okay, if we change the VP class to NET, will this not slow things down > significantly for all user connections ? Can anyone point out what benefits > (if any) changing the VP class will give us and which ones do you > recommend... > > TIA as always > > Sean