JMeter ramp-up Period (in seconds) description (concurrent concurrency possible)

Ramp-up Period (in seconds)

"1" Determines how long it takes to start all threads. If you use 10 threads and the ramp-up period is 100 seconds, JMeter uses 100 seconds to get all 10 threads up and running. Each thread starts 10 seconds (100/10) after the last thread is started.  The ramp-up needs to be long enough to avoid having a workload that is too large to start the test, and to be sufficiently small that the last thread starts before the first one finishes. General Settings ramp-up= the number of threads to start and adjust up and down to the desired.

"2" is used to tell JMeter how long it will take to establish all the threads. The default value is 0. If ramp-up period is not specified, that is, ramp-up period is zero, JMeter will establish all threads immediately. Assuming that ramp-up period is set to T-second, the total number of threads is set to N, JMeter will establish a thread every t/n seconds.

"3" ramp-up Period (in-seconds) represents how long it takes to execute, and 0 represents concurrent concurrency

Delay Thread creation until needed

Delays the creation of threads until the thread starts sampling, that is, any thread group delay and acceleration time after that is the thread itself. This can support more threads, but not too many are active at the same time.

Scheduler

When the scheduler is selected, you need to enter the start and end times. When the test starts, if it must jmeter wait for the start time to arrive. At the end of each cycle, the JMeter verifies whether the end time arrives, if it is, the run stops, and if not the test is allowed to continue until the iteration limit arrives.

In addition you can use the start Delay and duration text fields. Note the startup delay overrides the start time, and the duration overwrites the end time.