The test case developed for this problem presents itself in
different ways depending on the version of the server it seems.
On 11.70 it can be possible that after a shrink operation
happens on a table with an attached index (the shrink must
release pages) further actions on this table which cause it to
expand again (so it would have to grow out of the extents left
after the shrink) might cause assert failed page check errors.
In the assert failure file you would likely see the following
type information:
08:55:58 bfcheck: bad page: pg_flags #### != type 0x10
When you look at the page header you might notice that the page
offset for the page address matches disk, but that page offset
does not belong to the table the error is being reported again.
This is happening because of an internal cache of buffer
information is not being invalidated after the shrink so that
when the table grows again (after the shrink) the old cache
information might be accidentally referenced again but this old
information is pointing to pages which are no longer part of the
current tables extents. Thus the likely page check/bfcheck bad
pg_flags assertion.
At this point, if the server would be restarted, the issue is
resolved as there is no physical corruption (which would
normally be what a page check/bfcheck error would normally
indicate).
On version 12.10 the problem presents differently (different
type of assert failed) and also in 12.10 the index on the table
has to be a detached index, as the shrink operation is not
allowed to execute on a table with an attached index. So in
12.10, if you have a table and a detached index, and you run
the shrink fragment operation on the index partition, and it
gives up pages, and again, you then grow the index (so it has to
extend again) if it doesn't re-grab the same pages, the same bad
cache information can happen. However, on 12.10, it would seem
the type of failure that is seen is a SEGV, to the assert failed
looks more like this:
Assert failed: No Exception Handler with a stack trace that
looks like this:
bycmpr()
bycompare()
updp_shuffle()
btcpybck()
btusearch()
btadditem()
rsbtadditem()
fm_idxinsert()
fmwrite()
aud_sqiswrite()
chkrowcons()
addone()
insone_next()
doinsert()
sq_putinsert()
sqmain() |
