RELATIONSHIPS:  DEVICE  DHF, DMR, DHR

Caveat.  There are many ways to meet the requirements of the Design History File (820.30); the Device Master Record (DMR, 820.1811); and the Device History Record (DHR, 820.184) required by the Device CGMPs.  The following is one field tested approach.
Many  companies start a new DHF for major changes to their device.  If minor changes they handle under the CGMPs (Change Control, 820.40(b)).  
As with most of the points discussed herein, there are more than one correct approach.

Generally I recommend to my clients if they ask, that the DHF be used for major changes (with each new major change an addendum to the original DHF, or a new, cross-referenced DHF), which require some type of control of a series of development changes per 820.30.  For a minor / simple change, I recommend change control under  820.40(b), which at most companies is under a Change Request / Change Order (the CR when approved, can become the CO).  To it are attached the verification / test info'n / references, e.g., test report number / Lab Book Project no. etc, to justify the change, or in very simple changes, the actual data on the CR / CO.  The CO needs to have a block referencing a check for need to file a new 510(k) per Memorandum K97-1, and also tied to some kind of list / log of changes for a cumulative change review as well per that same K97-1.  All this is filed in Document Control, usually under QA (as would a closed out DHF, in many companies).  Of course this requires that document changes be defined in such a way to allow device changes (which are usually driven by a document change anyway, e.g., drawing change, specification change, etc.). 

When there is fielded software (firmware or software) and a revised version is created under change control, how does this affect the DMR and/or DHR?
Any change to a product, hardware or software, requires a change to the DMR (under change control, 820.40) for that product). Often the DMR includes a DHR template / blank (may be a "traveler" template /  blank, or in addition to a traveler), which would also be changed, or would at least drive a change to the DHR anyway, reflecting the new Revision / Release nos. of the software so changed (unless the Rev / Release No. entry is a fill-in blank). 
Consider the situation where a company has updated software that is then sent out to their customers.  In such a case, one possibility is that both (DMR and DHR) are updated (the DMR drives DHR content), assuming that the software is changed across the board.  If you're changing software for one customer at a time, then you're furnishing custom software, each program unique to each customer, and your entire CGMP system would have to be designed under that system.  My discussion is focused on the assumption that the software is a rev / rel where all customers for that particular software get the updates, new revs / releases. 
  
To clarify the role of the DHF, DMR and DHR:  The DHF shows the development of the device proving that the 8 other requirements of 820.30 Design Control have been met in its development from the "start" date.  The DMR is one result or design output from the DHF documented activities.  The DMR (820.81) is the device description, or "recipe": basically a list of all controlled records ("living documents") that define the device, to allow it's replication as defined in the FDA clearance (510(k)) or approval (PMA) documents.  The DMR might list device drawings, assembly work instructions / SOPs, test instructions / SOPs, BOM blanks (part numbers and part / component descriptions with blanks for quantity and lot numbers), blank travelers (which may list applicable validated / verified equipment settings with blanks to be filled in with the actual settings, operator or QC signatures and dates, and similar), reference other device specific SOPs, labels, Instructions for Use.  Some DMRs may list the generic SOPs that also apply to that device (and other devices), but don't have to. It would include the DHR template if additional to the above, e.g., traveler.

Additional on the DMR (the device "recipe"):  Although riskier, you could structure the DMR to list the device controlling documents without their current revision nos. / dates (e.g., list Drawing No. 0123, "current revision"; or SOP XYZ, "current revision” ).  Then the DMR would not always have to be updated when the device or software has minor changes, or even some major changes. However, the actual DHR template would have to be updated to reflect using the most current documents / settings / parts , et al, during manufacture of a lot.  All such changes would be under Change Control per 820.40.

The DHR (820.184) is the lot build history for one production lot; a record of how one lot / batch (lot number), or one serial number was built, quantities, RM lot nos, dates, personnel involved where appropriate, proving that that lot followed the "recipe" outlined in the DMR.  It would have the filled in / signed BOM, a filled / signed traveler (which could be a "DHR template blank"), samples of labels / IFUs included, sterile lot info (if sterilized), etc., showing / proving conformance to the DMR developed by the manufacturing process recorded in the DHF. Prior to release of that lot to the field, it would be reviewed and signed by QA, who would assure its accuracy and completeness of data and required enclosed documents.
In essence:   -- the DHF > DMR > DHRs.  See also "Definitions", 820.3.
The ultimate approach taken by a company must be defined by an SOP(s) and then followed!
-- John E. Lincoln, jelincoln.com

Note:  FDA's K-97 has been replaced by two FDA Guidance Documents  on changes to Devices / Software Requiring a new 510(k). JEL

Further updates: 06/20/2022 - JEL