That is correct. One minute is the setting in the install guide because it is the most frequent setting that a Windows Task allows. If I were able I would even set it lower, but that's currently not possible in Windows tasks.
It needs to run as frequently as possible for several reasons:
1. Tableau Server schedules can be run as frequently as every 15 minutes. Therefore if you run the task every 30, and a user sets up a VizAlert on a 15-minute schedule (assuming you set one up), they will not get their alert when they expect.
2. Any user who authors a View can use the "test_alert" comment at any time, which is intended to trigger the alert instantly. If it runs a half hour later than they enter the comment, that's not really "instantly"! With the one-minute setting, they usually get the email in two minutes or so (still not as fast as I'd like, but reasonable).
3. When you stop VizAlerts, then start it back up again, it will attempt to run alerts that were skipped immediately on the next iteration. That may be important to do right away, rather than a half-hour after the fact.
4. Finally, because "why not?". All it does every time it runs is run a sub 1-second query against the PostgreSQL repository--it's not expensive at all.
So all that said, you certainly can run it less frequently if you like--that's up to you. But I wouldn't recommend it, generally speaking.
Matt Coles your points are very helpful. Thank you. One more question.
Lets assume that i have set vizalerts subscription for 100 workbooks out of 145 workbooks published to the server. Does the amount of resource used for running the script increase too? TIA. This is super exciting!
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The amount of work needed to actually run the script is minimal. All the real work is done by Tableau Server. If you have 100 subscriptions you're running with VizAlerts, then the amount of resources needed to process all of them will be greater than the amount needed to process a single alert. But on the script side, it's not going to need much. It's going to end up hitting your Tableau Server instance the most. If they're frequently-running alerts that take a long time to render, then even more so. Mind you, the script will only push work to Tableau Server when the alerts are actually scheduled. So if they only run once a week, then all week long, VizAlerts will only be querying PostgreSQL and requesting a test trusted ticket--no big deal. Once you hit the time they were scheduled for, however, is when VizAlerts will start requesting CSV and PNG and PDF exports of the vizzes from Server.
Note that at that number of subscriptions, you're likely going to need to start running multiple instances of VizAlerts to make sure you are processing them quickly enough. But that's a ways out.