DirSync - or the Microsoft Online Services Directory Synchronization Tool, to give it it's full name is the tool that ensure your on-premises Active Directory and Exchange organization are in sync with your cloud services from Office 365.
Sometimes though, the default schedule of every three hours just isn't enough. Perhaps you're building a test environment and need to ensure changes are propagated to Office 365 quickly; or your internal process dictate that very soon after the addition of a new Active Directory account and remote mailbox, the user can log in.
Fortunately though, it's easy to reduce the schedule DirSync uses. To reduce the schedule, we'll perform the following actions.
First, navigate to the following directory on your DirSync Server:
C:\Program Files\Microsoft Online Directory Sync\
In this directory we'll find the main service executable that is used to run the DirSync schedule. It's associated Microsoft.Online.DirSync.Scheduler.exe.config file contains the configuration settings that determine how often it runs. Open this file in your favourite text editor, or if you have one an XML editor.
Locate the following lines within the Microsoft.Online.DirSync.Scheduler.exe.config file:
<add key="SyncTimeInterval" value="3:00:0" />
You'll see the frequency of the schedule in the format 03:00:00. This means that it performs a synchronization job then upon completion waits a further 3 hours until it performs the next run.
Edit the time within this file to reduce the sync schedule; for example to reduce the time to every 30 minutes use the following values:
<add key="SyncTimeInterval" value="0:30:0" />
Once you're happy with the changes, open the Services console (Start>Run>Services.msc) and restart the Microsoft Online Services Directory Synchronization Service.