Several times I have ran into the following issue with an event being logged in the vCenter Server event log every minute:
Active Directory Web Services encountered an error while reading the settings for the specified Active Directory Lightweight Directory Services instance. Active Directory Web Services will retry this operation periodically. In the mean time, this instance will be ignored. Instance name: ADAM_VMwareVCMSDS
I had fixed this on several vCenters that I managed. However the problem returned on one vCenter this weekend after enabling vCenter Linked Mode. I decided to document the solution here so it is easier to find if I run into this problem again.
As described here this is caused by a simple registry setting. Browse to the following key:
Delete the existing key (string) for “Port SSL” and replace it with a DWORD named “Port SSL” with a value of 636 (in decimal).
Restart ADAM_VMwareVCMSDS and ADWS services. Problem solved.