@SreedharRayankula

As per my understanding, Obj-* methods should be able to get the data from any table that conforms to PRPC internal table structure (presence of pzInsKey, pxObjClass, pxUpdatedateTime etc.) as long as your PRPC instance can connect to the database holding that table (via Data-Admin-DB-Name).

So, yes, in theory, 8.6 instance can read data from 7.x DB tables hosted elsewhere. PRPC as a tool is bound by standards of database software when creating a DB table or populating it with data. Only exception is the pzPVStream column where PEGA keeps the data using its own encryption/format. Data on exposed column of a table will always conform to the standards (e.g. varchar2) of DB software.

I'm not entirely sure if PEGA has made any changes to pzPVStream or the way Obj-* methods works internally (most likely it hadn't). But given that you are dealing with a production instance here, I would strongly suggest you to open a support ticket with PEGA to get it confirmed by them.

Alternatively, you may try to convince your Business to keep at least one 7.x node running that will just act as service node to fetch the 7.* data via API, thus avoiding this DB table structure related problem altogether. Depending on the frequency of service calls, that single node doesn't require the same level of hardware it is currently enjoying in production, as it will be used only to cater the service calls going forward, and not actual user sessions.

Hope it helps.