Selecting the correct GAMP software category

With reference to a Siemens Simatic S7 PLC can anyone advise me what GAMP software category this falls in. I have been told category 3 but believe it to be category 4. In addition can anyone explain the the difference in validation requirements for cat 3 and 4. Thanks.

Hi Pete,

Is it non configurable, has there being any modifications to it, or are you going to use it “out of the box”


Hi Graham,

Only the standard software modules/blocks supplied within the Siemens Sigmatic S7 software have been used. These have been configured to work in a particular sequence to semi automate a process. No modifications/customisation has been of the standard modules/blocks.
The S7 software cannot be used out of the box without configuration.



I have in the past validated Siemens Simatic S5/S7 PLCs for a major pharma within a secondary manufacturing environment. Specifically, a Glatt granulation suite utilizing Glatt multi-processors / fluid bed driers for a tableting facility.

As Graham has indicated, it really comes down to whether it’s out of the box (off the shelf) and installed, or configured for a specific clients needs. Very, very few are NOT configured for specific client needs (User driven), and therefore GAMP4 would apply in most cases.

All of my previous experience on PLCs, DCS or SCADA have been in the GAMP Category 4 area! i.e. you would need to consider conducting code reviews on the function and control blocks within the Siemens Simatic PLC (IQ); configuration verification type checks (IQ); static I-O listing verification (function blocks to field devices) (IQ); Module(s) verification; I-O loop testing (dry and wet) / functional / system testing (OQ) including all alarms and error messages; back-up and recovery (IQ); software baseline verification (IQ); I-O loop and field device calibration (IQ); FMEA on PLC i/p modules (OQ); logical and physical security (does the system produce electronic records e.g. for batch release?) (IQ).

The ‘system’ should be validated from ‘end-to-end’, don’t make the mistake of trying to break-out the software and validate it separately. It’s a downstream nightmare if you do and, in the end, is a nightmare approach that’s no cheaper. CSV is end-to-end ‘systems validation’ anyways.

Just my personal experience; others may have there own opinions.


According to GAMP firmware falls into Cat 2, and this is divided into

  • Non configurable
  • Configurable
  • Bespoke firmware which falls into cat 5
My first question is, is firmware regarded as being similar to PLC’s so would this methodology apply to PLC systems.

My second question is, if a PLC falls into Cat 2 does that mean reduced validation testing need only apply, or is it an unwritten rule to place PLC’s into cat 4 all the time.


  1. I don’t believe firmware is regarded as being “similar” to a PLC. So your methodology would not apply. Firmware in the context of GAMP talk tends to be embedded software type temperature controllers (e.g.), where you set an upper and lower parameter such as temperature control limits or a chart recorder. However, it is fair to say that a PLC would be considered firmware coming straight out of the box, up until the introduction of ‘Function Block(s)’/ladder logic, as the ‘Control Blocks’ and hardware are standard. But as soon as you introduce function block / ladder listing functionality for the end User, you’re into customization / configuration changes that fall within GAMP Cat 4.

  2. I know of nobody who has validated a PLC in Cat 2, because the PLC is “useless/very basic” out of the box until you introduce the function blocks/recipes etc.

Also, it is important to audit the suppliers programming standards and techniques before the code walkthrough.

According to The GAMP Good Practice Guide: Validation of Process Control Systems, A PLC is an embedded system which could contain software components belonging to multiple GAMP catagories (Firmware GAMP catagory 2 with configuration parameters, and the Ladder Logic GAMP catagory 5). I would consider the complexity of the system (simple: skid mounted mixer to more complex: Sterilizer). For any I would conduct a supplier audit of the system integrator that would be writing the PLC code and configuring the system. I would then do module or unit testing of the PLC ladder logic. Then a FAT to demonstrate that the PLC, user interface, recorder, and process equipment operate correctly.


That clears it up for me.


I always found that there was very little difference in the qualification of GAMP 3-5 systems. Plus, you don’t often get a straight 3 system. Based on that, I pretty much threw out the whole GAMP classification system and based the validation on the Risk, then defined the approach in the Validation Plan.

Just like Dave, I would not recommend splitting the PLC from the system.

PLCs - Won’t do anything without code and they aren’t firmware. So it all comes down to where did the code come from? For instance, I could buy an autoclave and call the code COTS. (CAT4) Why? Because I bought their off the shelf autoclave (they make 100s with the same code). But? I could buy a different autoclave and request them to program the PLC to meet my specifications. Now I have a custom system. (CAT5) For both of these systems, I will need an interface. The interface can be used to change the configuration of the code in the PLC.

I’ve seen people consider the PLC a black box and only test the code via the operator interface. Not a very good method, but the PQ passed so there was no reason for an auditor to go any further.

Hi Guys,

Reading the various comments posted it appears to me the following statements sum-up software catgegory 3, 4 & 5 of GAMP4.

Cat.3 - Off the shelf software that needs no configuration other than setting paramaeters…

Cat.4 - Proven software that cannot be used off the shelf without significant configuration of the modules. Source code is not modified

Cat.5 - Development software or software that requires custom programming of the source code to meet the customers requirements.

I would be interested to hear any fuurther comments you have on the subject.

Regards, Pete

This is probably best described with examples,

Cat 3:

  • MS Word
  • Excel
  • Minitab
Cat 4:
  • Trackwise's document management application (configuration)
  • Pilgrim Software's enterprise management suite (configuration
  • LIMS
  • Excel with modules ???????
Cat 5:
  • Camstar's MES solution (configuration and programming)
  • SAP (configuration and programming)
  • Most custom build devices used in the Medical Device industry
Please add to my list or correct me if I am incorrect.


Yes, you are the absolutely write.