Dead space in sessionid.tdb

Volker Lendecke Volker.Lendecke at SerNet.DE
Sat Aug 23 02:15:23 MDT 2014

On Fri, Aug 22, 2014 at 08:29:46AM -0700, Hemanth Thummala wrote:
> Hi Volker,
> We are running 3.6.12 + (critical and security fixes).
> Have seen few threads and patches related to cleaning up of messages.tdb
> and locking.tdb files. Here is one we found for cleaning up dead records in
> messages.tdb file
> But this is specific to messages.tdb file cleanup. Should we have similar
> cleanup routine for sessionid.tdb as well?
> Also would like to understand the reason for having huge dead record at one
> point. Any pointers here will be really helpful.

Well, this is for the recovery area inside a transaction.
tdb_summary counts that as dead. The fact that it is so
large might just be a bug that Rusty fixed a few years ago
with 5767224b7f4703c3195aa69eef4352d80980f95e and
3a2a755e3380a8f81374009d463cd06161352507. While searching
through the tdb commit log for these two I came across so
many fixes and performance improvements in tdb that I'd
really recommend just dumping the current tdb implementation
into your tree and use it. Freelist contention reduced,
freelist fragmentation improved, all sorts of improvements
all over the place. And it should be completely compatible.
If you want to really improve things, you might also look
at the mutex support, which dramatically changes things
under high load.


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