We have just completed an upgrade in our DEV environment to V15.4.1, which basically passed all our validation with only around 5 items that needed to be adjusted.
I then noticed that when an Object is updated in V15.4.1, it's _V view is no longer available and went back to the Release Note for V15.4 which include
This release mitigates an Oracle limitation in previous releases that reduced performance for object attributes. The limitation resulted from the use of _v views instead of _v2 views (odf_x_v2) in portlet queries. We updated the core add-ins including APM, PMO, PMBOK, PRINCE2, and NPD. We also recommend that you use _v2 views (odf_x_v2) for custom queries. Do not create _V views on bootstrap or attribute changes.
It should be more than a recommentation given that the _V views no longer are used, and in our case, the _V view was deleted from the database when the object was modified. The _V views existed in our DEV environment when we undertook our initial verification, and am now concerned that they may automatically get deleted in the future which will then impact on other custom code.
We are working with CA Support to determine if this is an anomolie with our environment, but initial feedback is that _V views won't be provided in this version.
When you plan to undertake your upgrade to PPM V15.4, and you have some customisation in your environment, you will need to consider if any of your code uses the _V views, and if so, will need to address it.