Question no.1) Can we consider PLC as a Electronic Record system? and why? Will it capable of storing data/values?how much data or days it can store? how to calculate that?
Question no.2) as per ISPE GAMP 5 guide line PLC software will fall under which software category? (Cat1, 3, 4 or 5)
Kindly let me know

Having been on dozens of Pharma automation projects, PLC software (the logic and data in the PLC) is definitely Category 5. Once in a while, with key-lock protection, standard PLC files/routines that can be compared against a "vault" version, configurable I/O and reusable subroutines, I can get Validation to treat the PLC as whole as a Category 4 system.

No, I would never be able to convince an FDA inspector (or a plant Quality or Validation manager) that the PLC can be used to store data. First of all, to meet 21CFR Part 11 requirements for data integrity, a PLC would need to have a time-stamp attached to each piece of data. Secondly, PLC data tables are easily manipulated online or offline, and the data storage limits in the PLC (2 Mb on average) doesn't go very far. It is much better to retrieve the PLC values and store them in a relational database, whether a custom SQL solution or a commercial historian product. The PLC, from a data standpoint, is essentially only as secure as a memory stick plugged into a PC, but with logic capability.

Dear Mr.Scott, Thank you so much for your quick response and clarification.
-> Is there any ISPE guide line which describes more about Process control system software & Hardware categories?
-> In ISPE GAMP 5 guideline the "Normal HMI software- HMI with out internal storage " booked under category 4 (Configured COTS Product) may i know the reason? as far as my concern is we are only doing RUN TIME CHANGES or ENVIRONMENTAL CHANGES only then why we are not considering it as Non Configured COTS product
->Briefly sahre your knowlede on the same sir for each category one process control system example and the reason? Thanks in advance