Today I had to work with a really old svn repository again, which was still in the old bdb format (not in the newer and recommended fsfs one). This caused quite some problems, like, um... you cannot checkout, update, or commit anything.
$ svn co file:///path/to/myrepo
svn: Unable to open an ra_local session to URL
svn: Unable to open repository 'file:///path/to/myrepo'
svn: Berkeley DB error for filesystem '/path/to/myrepo/db' while opening environment:
svn: DB_VERSION_MISMATCH: Database environment version mismatch
svn: bdb: Program version 4.6 doesn't match environment version 4.4
A quick search revealed that this is bug #342508, a solution is/was supposedly mentioned in /usr/share/doc/subversion/README.db4.3 (which does no longer exist in the Debian unstable package). Luckily this blogpost has some details.
So, the short HOWTO for upgrading an svn repository of one Berkeley DB version to another one is:
$ cd /path/to/myrepo/db
$ db4.4_checkpoint -1
$ svnlook youngest ..
$ db4.6_archive -d
In this case I upgraded from 4.4 to 4.6 (do "apt-get install db4.4-util db4.6-util" if necessary).
While I was at it, I also switched the repository to the fsfs format then:
$ svnadmin dump /path/to/myrepo > myrepo.dump
$ mv /path/to/myrepo /path/to/myrepo.bak
$ svnadmin create --fs-type fsfs /path/to/myrepo
$ svnadmin load /path/to/myrepo < myrepo.dump
Maybe this is helpful for some other people out there.