Sometimes Informatica workflows when triggered can go into a waiting state instead of a running state. This usually happens when there are a number of workflows running in parallel.
Informatica admin console has a property where the Admin can define the maximum number of concurrent sessions that can run on the server. It is decided based on the capacity of the server by the Admin. However by default it is set to 10 which should suffice most production scenarios.
This property limits the maximum number of workflows that can run at any given time. Increasing the value can allow more number of sessions to be executed in parallel but should be done only after considering the current capacity and load on the server.