If you have a query that uses OLAP functions that have to write
data to temp tables created in your temporary dbspaces, and the
system is configured to use kaio then the writes to these
temporary tables will fail due to improperly aligned buffers,
causing the query to fail with just a -768 error. To use kaio
for your temporary dbspaces, the temporary dbspace must be in a
raw or block special device (so not a file system file and using
kaio by enabling DIRECT_IO...in these cases, the server will do
kaio to regular dbspaces, but IO to temporary dbspaces, created
with the -t flag, will use aio instead).
Stack if you set a trap for the 768 error:
sqerr
sqerr1
olap_pbyoby_next
sort_open
sort_open
filltemp
scan_open
materialize_viewtmp
materialize_viewtmp
materialize_viewtmp
materialize_viewtmp
materialize_viewtmp
materialize_viewtmp
materialize_viewtmp
prepselect
open_cursor
sql_open
sq_open
sqmain
spawn_thread
th_init_initgls
startup
The frame of interest is olap_pbyoby_next, which shows the query
is doing some OLAP function...unfortunately the
olap_temptab_write() function already returns before the -768
error is reported so you can not see it on the stack.
From onstat -g ath you can see kaio threads, which indicate the
server is using KAIO:
Threads:
tid tcb rstcb prty status
vp-class name
32 4b291400 0 3 IO Idle
1cpu* kaio
38 4b439560 0 3 IO Idle
8cpu* kaio
39 4b4398a0 0 3 IO Idle
10cpu* kaio
Then output from lsof (on Linux) which verifies the temporary
dbspace is using a block special device, so kaio would be used
to write to that device:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
oninit 12246 root 256u BLK 253,19 0t0 6581
/dev/mapper/vg01-lvol12
oninit 12246 root 257u BLK 253,25 0t0 6976
/dev/mapper/vg01-lvol19
oninit 12246 root 258u BLK 253,20 0t0 6645
/dev/mapper/vg01-lvol13
oninit 12246 root 259u BLK 253,21 0t0 6698
/dev/mapper/vg01-lvol14
oninit 12246 root 260u BLK 253,22 0t0 6762
/dev/mapper/vg01-lvol15
oninit 12246 root 261u BLK 253,26 0t0 7040
/dev/mapper/vg01-lvol20
oninit 12246 root 262u BLK 253,6 0t0 5563
/dev/mapper/temp-lvol1 |
