Hi Richard:
Yes this is interesting to me as well. And once again, as so often happens when reading the bible, there are conflicting images that are presented and come into tension.
On the one hand we have, for example, the very moving story of Jesus and the “woman taken in adultery”. He seems to be scrupulously guarding her privacy here; a real “gentleman God” if you will. No, (reader, onlooker) it’s none of your business.
Then we have those texts where God casts our sins to the depths of the sea; and He says further He “remembers them no more” sort of language.
And this is all very wonderful and comforting and encouraging isn’t it. It’s as if God is saying HE certainly won’t be holding anything against us! That’s good news; the barriers between us and Him are not His doing.
However…
We also have the ideas of God keeping track of stuff; Revelation speaks of books. Opens the books. (eg Rev 20:12 – “And I saw the dead, the great and the small, standing before the throne, and books were opened; and another book was opened, which is the book of life; and the dead were ***judged from the things which were written in the books, according to their deeds.***” I’m talking of the judgement language and passages. An unmistakable image of God keeping records clearly comes to mind. I mean without records, how else can judgement be conducted? Are we saying that God is a destroyer of evidence? (Which itself is a crime in our own culture and time!)
Hence we have tension: God destroys the records, up until the time He needs them again and they mysteriously reappear?? I clearly resonate with the passages where God keeps no records of our wrongs… yet my Penal Sub friends clearly resonate with those where records ARE kept.
Well, what about Joshua the high priest standing before the angel of the Lord in Zechariah 3? – we could say that the one who accuses, Satan, is the one whose “records” are being used. But this of course prompts a rebuke from the Lord.
Which brings up yet another problem. When we read that God keeps no records of our wrongs, are we actually suggesting that God literally wipes His memory clean of historical events? (like a hard drive that one moment has information – the next it doesn’t…?) That surely can’t be can it? I certainly can recall, and clearly, that day I stole, or lusted, or was prideful or unforgiving or any of a host of behaviors I’d really truly want to obliterate from memory. It happened. Period. Sorry. History is “un-eraseable”.
Is this all just an elaborate fiction then? Hyperbole to make a point? God “forgets” (wink wink!! 
It’s an interesting dilemma.
For myself, I think this can be resolved in much the same way we resolve God’s claim that He won’t (can’t) forgive us unless we forgive others. Which is to say that, for forgiveness to be truly beneficial to me, I must relinquish my “right” to withhold it from others, all the while desiring it’s benefits for myself. To think that way has missed the point. I myself can neuter the power of forgiveness simply by refusing to participate in it. God’s forgiveness of me “works” only when I comprehend that I am to be transformed into a forgiving person – ie one who does not hold it against the one who sinned vs me.
Same with “forgotten sin”. It is not God who keeps it “alive” by keeping records of it; it is we who keep it “alive” (ie recorded) by clinging to our selfish rebellion and distrust. So, when we love like God loves, we too begin to “forget” those ways – having replaced them with the ways of love. Sin having been suffocated out of existence due to lack of attention and oxygen so to speak!!!
Or something like that…
Bobx3