Many Actions allow to select how often they are to be executed:

• Once only = execute exactly once on each client (for customers that use MarvelClient Roaming, once executed, an action will not execute again on clients users roam on/over to, as the actions.xml is roamed along, memorizing Actions that have already been executed. For non-MC Roaming customers, an Action set to run "Once only" will execute once as per actions.xml file).
• Once a day only = execute once a day; whilst for most users there is no difference between persisent (=at every relevant Runtype) and Once a day only, as they only start their client once a day, for Administrators and Developers this may well make a difference for Actions that e.g., prolong client startup, as they tend to restart their clients multiple times a day.
• Once from start to end = only makes sense if an Action is configured to run at or referenced from within multiple Runtypes; in case an Action is likely to run more than once from client start to shutdown, but should in fact only be executed once, this option comes in handy. An example would be configuring an agent to run at "Background - Init", "Background" and "Shutdown" without wanting it to run three times - users who are yet to start their client will run the agent in "Background - Init", users who have their clients up and running would run the agent at next background run, and users who close their client before their next Background run will run it at shutdown.
• Persistent = run the Action whenever Runtypes and conditions match

NOTE: Selecting any of the "Once ..." options displays a check box "Keep local exec. info" underneath the Repeat option:
If "Keep local exec. info" is checked, re-saving an Action will not reset the counter as to how often a particular Action has already been executed on a client - for e.g. a "Once only" Action this means that it will not run again on clients where it has already been executed, even if the configuration has changed(!).
If "Keep local exec. info" is NOT checked, re-saving an Action will reset the counter as to how often a particular Action has already been executed on a client - for e.g. a "Once only" Action this means that it will be executed again on all targeted clients (naturally according to the Who tab and where conditions match according to the When tab).

NOTE: Some Actions have "Once only" as the default repeat setting, most are set to run permanently by default.