if VM is deleted from vCenter it is not deleted from Servicenow virtual machine instance table

[Nancy19]

If a VM is removed from vCenter, and after that discovery is run in ServiceNow, that record is not removed, thus the old data remains in the table with the wrong state.

[Mike Allen]

It is now considered a stale CI.  ServiceNow leaves it up to you what to do with Stale CIs.  Some delete them, some move them to a state of Retired, or whatever.  I try never to delete CIs, as there may be a lot of relationships that rely on that CI, and deleting it can mess with reporting.

[Nancy19]

I wrote a business rule on the stale CI table, which deletes the VM from CMDB table if that VM is found in the stale CI table.