We do a lot of bulk loading, so we picked a time during the day to shut MonetDB down and restart it.

The reason, memory fragmentation, does occur and in our experience would cause the database to fail and lock up. It will stop accepting connections.

Our database health gradually and constantly decreases.  Although I can say we have never received wrong answers from the database or had any obvious effects from poor database health. We periodically recreate the entire database to get the health of the database back up to 100%.  Essentially we use MonetDB as a fast query database and not the primary database for maintaining the integrity of our data.  There is no repair utility for the database.  We're still learning how and if we should report issues like this because it happens gradually and the log has some splat marks " *** glibc detected *** /usr/bin/mserver5: corrupted doubly-linked list:  0x00007fa12411f4d0 *** and *** glibc detected *** /user/bin/mserver5: double free or corruption (!prev): 0x00007fa12411f4d0 *** in it.

Like anything else, I think you learn to live with whatever tools you are using and play into the strengths and avoid the weaknesses, reporting them and hoping they can get patched up eventually.

Brandon