Thanks for the response and the pg_xlogdump tip. Dave > On May 20, 2016, at 2:35 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > > Dave Stibrany <dstibrany@xxxxxxxxx> writes: >> There are 98 WAL segments in the directory currently. > >> From the documentation, I understand that the number of WAL files can go as >> high as (3 * checkpoint_segments + 1) segment files, which would be 97 in >> my case, but I seem to be consistently at this number or even higher >> (sometimes over 110 files) and I don't think I've ever seen the directory >> smaller than ~97 segment files. > > I don't believe there's any aggressive attempt to remove segment files > after transient peak usage (what happens to them instead is explained > below). If you had many times the expected number of segments, I'd be > worried, but these numbers sound pretty normal to me. > >> Regarding the ordering of segments, my understanding is that segment >> 0000012000003720000008B would be written to after 00000012000003720000008A, >> but the timestamps (14:59 and 15:06, respectively) appear to show >> otherwise. There are several cases like this. Does this mean that >> 00000012000003720000008A has newer WAL records than >> 00000012000003720000008B?? > > No, it probably means that neither one has been written at all yet. > Typically, when a WAL segment is deemed no longer needed, the file isn't > physically removed but is merely renamed into place as a future segment. > The idea is to reduce unnecessary filesystem work as we create and delete > WAL segments. You could check this out if you have pg_xlogdump at hand, > by seeing whether the WAL file's first page header claims to belong to the > segment indicated by the file name, or to some much-older segment. > > regards, tom lane -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
