In vCenter 6.0, a new table called VPX_HOST_TEXT is created in the database and populated with entries from VPX_TEXT_ARRAY.
This issue occurs if there are host entries in VPX_TEXT_ARRAY without a matching host ID in VPX_HOST.
To determine if the VPX_TEXT_ARRAY table has host entries without a matching host ID in VPX_HOST, run this SQL statement:
SELECT * FROM VPX_TEXT_ARRAY WHERE MO_TYPE='host' AND MO_ID NOT IN (SELECT ID FROM VPX_HOST);
This SQL statement returns 0 for a healthy database.
If this statement returns any other value, the VPX_TEXT_ARRAY table must be fixed before the upgrade.