Monitor the virtual processors to determine if the number of virtual processors configured for the database server is optimal for the current level of activity.
You can use the following command-line utilities to monitor virtual processors.
Use the onstat -g glo option to display information about each virtual processor that is currently running as well as cumulative statistics for each virtual-processor class.
The vps field in the output shows the number of virtual processors currently active for that class. In the sample output for onstat -g glo in Figure 3, the vps field shows that 3 CPU VPs are currently active.
Use the onstat -g rea option, as onstat -g rea describes, to determine if you need to increase the number of virtual processors.
MT global info:
sessions threads vps lngspins
1 15 8 0
Virtual processor summary:
class vps usercpu syscpu total
cpu 3 479.77 190.42 670.18
aio 1 0.83 0.23 1.07
pio 1 0.42 0.10 0.52
lio 1 0.27 0.22 0.48
soc 0 0.00 0.00 0.00
tli 0 0.00 0.00 0.00
shm 0 0.00 0.00 0.00
adm 1 0.10 0.45 0.55
opt 0 0.00 0.00 0.00
msc 1 0.28 0.52 0.80
adt 0 0.00 0.00 0.00
total 8 481.67 191.93 673.60
Individual virtual processors:
vp pid class usercpu syscpu total
1 1776 cpu 165.18 40.50 205.68
2 1777 adm 0.10 0.45 0.55
3 1778 cpu 157.83 98.68 256.52
4 1779 cpu 156.75 51.23 207.98
5 1780 lio 0.27 0.22 0.48
6 1781 pio 0.42 0.10 0.52
7 1782 aio 0.83 0.23 1.07
8 1783 msc 0.28 0.52 0.80
tot 481.67 191.93 673.60Use the onstat -g rea option to monitor the number of threads in the ready queue. The status field in the output shows the value ready when the thread is in the ready queue. The vp-class output field shows the virtual processor class on which the thread executes. If the number of threads in the ready queue is growing for a class of virtual processors (for example, the CPU class), you might have to add more of those virtual processors to your configuration. Figure 4 displays sample onstat -g rea output.
Ready threads: tid tcb rstcb prty status vp-class name 6 536a38 406464 4 ready 3cpu main_loop() 28 60cfe8 40a124 4 ready 1cpu onmode_mon 33 672a20 409dc4 2 ready 3cpu sqlexec
Use the onstat -g ioq option to determine whether you need to allocate additional AIO virtual processors. The command onstat -g ioq displays the length of the I/O queues under the column len, as Figure 5 shows. You can also see the maximum queue length (since the database server started) in the maxlen column. If the length of the I/O queue is growing, I/O requests are accumulating faster than the AIO virtual processors can process them. If the length of the I/O queue continues to show that I/O requests are accumulating, consider adding AIO virtual processors.
onstat -g ioq AIO I/O queues: q name/id len maxlen totalops dskread dskwrite dskcopy adt 0 0 0 0 0 0 0 msc 0 0 1 12 0 0 0 aio 0 0 4 89 68 0 0 pio 0 0 1 1 0 1 0 lio 0 0 1 17 0 17 0 kio 0 0 0 0 0 0 0 gfd 3 0 3 254 242 12 0 gfd 4 0 17 614 261 353 0 onstat -d Dbspaces address number flags fchunk nchunks flags owner name a1de1d8 1 1 1 1 N informix rootdbs a1df550 2 1 2 1 N informix space1 2 active, 32,678 maximum Chunks address chk/dbs offset size free bpages flags pathname a1de320 1 1 0 75000 66447 PO- /ix/root_chunk a1df698 2 2 0 500 447 PO- /ix//chunk1 2 active, 32,678 maximum
Each chunk serviced by the AIO virtual processors has one line in the onstat -g ioq output, identified by the value gfd in the q name column. You can correlate the line in onstat -g ioq with the actual chunk because the chunks are in the same order as in the onstat -d output. For example, in the onstat -g ioq output in Figure 5, there are two gfd queues. The first gfd queue holds requests for root_chunk because it corresponds to the first chunk shown in the onstat -d output in Figure 5. Likewise, the second gfd queue holds requests for chunk1 because it corresponds to the second chunk in the onstat -d output.
If the database server has a mixture of raw devices and cooked files, the gfd queues correspond only to the cooked files in onstat -d output.
To monitor virtual processors with ISA, click on the VPs page on the main ISA page. ISA uses information that the onstat -g glo command-line option generates. Click Refresh to rerun the commands and display fresh information.
You must connect to the sysmaster database to query the SMI tables. Query the sysvpprof SMI table to obtain information on the virtual processors that are currently running. This table contains the following columns.