Q: What’s the impact of a user having lots of Shared calendars opened or just configured in his Outlook profile ? Is the calendar connection opened “on access” or is the connection made everytime the user opens Outlook ? What if the Outlook (2010, 2013) user has checked the “download Shared folders” to cache all Shared folders locally ? Are all calendars downloaded as the user opens Outlook ? Or is the download in the OST of Shared Calendars done on access basis only?

Screenshot 1: this is the place where you activate cached mode for Shared Folders as well (Outlook 2010, 2013)


Below are a few elements of answers, based on tests and real life expériences:

1- If the user didn’t have cached mode enabled for Shared Folders, but already had 10 calendars configured on their profile, and then if later on we enable cached mode for Shared Folders, these 10 calendars will be “downloaded” onto the OST file when users access these only – not all at once.

2- If the user has already cached mode enabled for Shared Folders, it’s when they will add each calendar that Outlook will download a copy of the calendar the first time. But if they uncheck the box beneath the shared calendar name, and don’t access it for a while, and then after 1 month they check the box beneath this shared calendar because they need to access it, Outlook will update the data with the data from the last month since last time they accessed it. Updates download of calendars is on access only when “Download Shared folders” is checked on Outlook (2010, 2013)

As a summary, if the user has cached mode enabled, calendars will be updated when they will access the calendar, if users doesn’t have cached mode enabled, calendar connection will be on access only as well.

So in conclusion, the calendar update (for cached mode) or calendar access (for online mode) occurs only when the user clicks on the calendar or switches from the “Mail” view to the “Calendars” view.

Quick illustrations below:

Screenshot 2: the bar where you switch from Mail-only view to Calendar-only view => changing this, if in the “Calendar” view you checked a few calendar, connection (online mode) or update (cached mode for Shared Folders) will be triggered for the checked calendars only


Screenshot 3: the calendar view with the list of calendars: only the checked ones will be accessed (online mode) or updated (cached mode for Shared Folders)