Do you have RT subscription for 100 symbols? What slows you down is probably that you might have exceeding subscription limit and constant subscribes/unsubscribes to RT stream get stuck at eSignal Data manager. If that is the case, you should up your subscription to the number of symbols you run scan for.
Expecting from AmiBroker to scan 100 stocks using realtime plugin and limiting its streaming-subscribed symbols to 30 is illogical, very illogical... It is like expecting from a car with a speed limiter set to 30 mph going 100 mph... You can try restarting the car, going backwards etc, but the simplest solution would be just getting rid of the speed limiter ...
I recommend reading this thread:
Besides if scanning only 100 stocks takes 15 seconds, I guess, that either your code is very ineffective or you don't use quick AFL in Automatic Analysis. It wouldn't be an issue if such scan was performed rarely, but if it is repeated every minute, it is a waste of computer's resources.
My understanding was that having a limt of 30 symbols meant that Amibroker would split a scan for say 90 symbols into 3 separate scans in order to avoid going above the subscription limit. And it would unsubscribe the previous 30.
Also I’m not sure why the RT plugin is used in the exploration analysis. What if I needed to scan 5000 symbols?
Sounds like I always have to stay within the max symbols subscription limit as they don’t get unsubscribed.
It's your choice if AmiBroker uses realtime plugin or local database. If you use local database, you can scan any number of stocks that you want without any issues. Also compare the time needed to complete the scan. If your code is effective, a Scan or an Exploration on local database, should be performed (a lot) faster.
Your understanding is incorrect. As absolute necessity this "symbol limit" in Configure screen must be set to your subscription limit minus 1 AND you must NOT exceed number of symbols in single scan beyond that limit.
If you have set it to 30 symbols and scan 100 it would mean that there is constant subscription/unsubscription to RT data happening which is prohibited by eSignal. And eSignal data manager actively discourages such abuse by SLOWING DOWN responses to such requests.
The very same rule applies to all RT sources that have limits on number of symbols. Abusing data provider rules by frequently watching/unwatching would bring you trouble and in extreme cases may lead to account termination.