Overall, ZipGrade utilizes server pools that allow the service to dynamically size to meet the current demand. As more users utilize the ZipGrade.com website or syncing service, additional servers and resources are added. However, it can take a few minutes for these additional resources to come online. Therefore, there is a limit to the number of new "open submission" student sessions that may being a testing session at the same time.
If more than 150 students attempt to start the same quiz within a few minutes of each other, subsequent attempts will receive an error message asking the students to wait a minute before trying again.
If you are using the open submission option to administer a quiz to more than 150 students, we recommend:
* Allow students to start the quiz over a range of time (at least 20 minutes) instead of instantaneously,
* Create separate quizzes with separate URLs (with possibly different questions) for groups of students to keep below the 150 student count
* Implement the quiz as a 'verified submission' quiz.
There is no limit to the testing sessions when using verified submission as the system is able to forecast the number of servers to add and when to meet the assigned time and class for each quiz.