# Forward Compatibility for Transaction Logs **URL:** https://forums.foundationdb.org/t/forward-compatibility-for-transaction-logs/1269 **Category:** Development **Created:** [March 30, 2019, 2:17am UTC](https://forums.foundationdb.org/t/forward-compatibility-for-transaction-logs/1269 "2019-03-30T02:17:15Z") **Posts on this page:** 1 **Showing post:** 3
### Author: ![alexmiller](https://sea1.discourse-cdn.com/foundationdb/user_avatar/forums.foundationdb.org/alexmiller/32/326_2.png) [@alexmiller](https://forums.foundationdb.org/u/alexmiller) #### Post date: [April 1, 2019, 10:31pm UTC](https://forums.foundationdb.org/t/forward-compatibility-for-transaction-logs/1269/3 "2019-04-01T22:31:21Z")
> [@dave](#): > > I have a couple of concerns about this feature from a UX perspective, though. It doesn’t resolve all problems with downgrades and it is very low level. So I would like to discuss a design for full forward compatibility. > … > The log version is selected automatically to be the highest version permitted by the minimum downgrade version. This is a “feature” that was intended to be incomplete and low level, as I attempted to preface in the background. This is work that’s being done with the goal of eventually being a part of some larger “Forward Compatibility for FDB” design, like you’ve laid out. I don’t really see `log_version` sticking around in the long term, as it should be superseded by something like the “minimum downgrade version” support. This chunk of the work is being done now to prevent incoming tlog changes from being the reason that one can’t roll back from 6.1.X to 6.0, if testing turns out that there’s nothing else blocking that. Once something like “minimum downgrade version” exists, transitioning off of `log_version` should be relatively easy. > [@dave](#): > > I’m not sure if there are any impacts on backup, etc. (I don’t think so.) Ah, [this thread](https://forums.foundationdb.org/t/fatal-error-corrupted-backup-data/1260/5) seems to suggest that the answer is yes, which I also hadn’t thought about yet. Thanks! --- _[View the full topic](https://forums.foundationdb.org/t/forward-compatibility-for-transaction-logs/1269)._