Symptoms

1. Confluence incremental index does not run every 60 seconds (which it should do)
2. The daily index optimizer task, which should run at 2 AM, runs every day at a different time.

Cause

Confluence relies on the Virtual Machine's time from which it is running, and the VM clock is not in sync with an NTP server.

 From NTP Server known issues:

NTP was not designed to run inside of a virtual machine. It requires a high resolution system clock, with response times to clock interrupts that are serviced with a high level of accuracy. No known virtual machine is capable of meeting these requirements.

Resolution

Check your NTP Server and system clock synchronization parameters/configuration, to ensure they are in sync.

See:

• http://support.ntp.org/bin/view/Support/KnownOsIssues#Section_9.2.2.
• http://www.vmware.com/pdf/vmware_timekeeping.pdf