Comments on: Difference between concurrent and simultaneous vuser

By: Kamran Khan

Kamran Khan — Tue, 01 Jun 2010 08:03:05 +0000

@Jacintha
Introducing lr_rendesvous create concurrency at that point – the immediate next function will be executed at single point in time (causing maximum pressure/load on DB/app/web servers. web_concurrent_start statement can be used for concurrent execution of a series of steps as Manish quoted.

@Lina
First, change in controller to simulate 500 users doesnt mean 500 concurrent users.These are 500 simultaneous users (and could be 2 or 2 overlapping/concurrent users by chance)
User and VUser is same. Controller decides the number of VUsers to simulate and not script. If you mention 10 users_name in script and run controller with 100 (assuming multiple instances are possible) then you’re testing application with 100 Users.

Second, having multiple iterations for various actions doesnt mean additional users. 100 VUsers and 1000000 iterations each – will simulate a load of 100 vusers only.

Third, if you use random/once for pramaterization then provide unique data for order number/name (whatever is required to be unique) – if it is coming from server as response, you need to correlate your script.

I hope that addresses your issues – although pretty late.

Sincerely,
http://www.Kamran-Khan.net

By: Manish

Manish — Tue, 15 Sep 2009 13:02:09 +0000

The explanation you have give in vice versa. For ex: in load runner script, we have two function i.e. web_concurrent_start(NULL) and web_concurrent_end(NULL). These functions perform concurrency. Its like a rendezvous point when all the URLs get loaded concurrently while in rendezvous point all vusers loaded concurrently.

By: lina

lina — Mon, 03 Aug 2009 08:50:53 +0000

thank you that was so clear , however i have another problem in understanding concurent users , if i have a script with 100 vuser on yahoo 1) Login, 2) Check no of unread mails 3) Logout
and they iterate for taks no 2) twice and in the controller i edit to 500 Vuser to run conncurrently ? please confirm if the below is true :
1- 500 concurrent user will run
2- each with 100 vuser and it will iterate for task no 2) ( all will run as vuser squence at the script)
my question is:
If i use Pramaterization for vuser random/once/…etc the possibilty of use to run with multisessions that may cause conflict at DB side (if Vusers are submitting order for example)
how can i prevent that??

thanks

By: Ankur

Ankur — Tue, 03 Feb 2009 10:41:15 +0000

That's why I made it as a seperate post. There is a lot of confusion regarding these terms. You may want to check the ongoing discussion at the HP LoadRunner forums.

By: Jacintha

Jacintha — Fri, 16 Jan 2009 12:33:31 +0000

can you please revisit your statement. I guess the explanation given here is vice versa.Because normally the Simulataneous Users are always greater than concurrent users. when we take a banking application, simultaneous users would be 50000 users whereas concurrent users would be 5000 only.
Please correct me if i am wrong.