onstat -g iof Disk IO Statistics by Chunk/File

The onstat -g iof command displays the statistics for disk I/O by chunk/file.

AIO global files:
gfd pathname         bytes read     page reads  bytes write    page writes io/s
3   disk001          2162960384     1056133     646090752      315474      148.8
        op type     count          avg. time
        seeks       0              N/A
        reads       0              N/A
        writes      0              N/A
        kaio_reads  953358         0.0048
        kaio_writes 307332         0.0127

4   disk002          339486720      165765      3265743683584  1594601408  51.3
        op type     count          avg. time
        seeks       0              N/A
        reads       0              N/A
        writes      0              N/A
        kaio_reads  12954          0.0135
        kaio_writes 24421712       0.0195
.....
312 sp_2580ins.db

Output Description

Heading	Description	Format	See Also
gfd	The global file descriptor number for this chunk.	Dec
pathname	The pathname to the chunk.	Str
totalops	The total number of read and write operations that have occurred against the chunk.	Dec	onstat -D
dskread	The number of disk reads that have occurred against the chunk.	Dec
dskwrite	The number of disk writes that have occurred against the chunk.	Dec
io/s	The number of I/Os per second.	Flt
op type	Type of operation.	Str
count	Number of times the operation occurred.	Int
avg time	Average time the operation took to complete.	Flt

Notes

The global file descriptor (gfd) values begin at 3. 0, 1, and 2 are used internally by Informix Dynamic Server for stdin, stdout and stderr, respectively.

If the above example, gfd=312 is a SPL debug file

Monitoring and Tuning

Examination of the values in each of the operations columns (totalops, dskread, dskwrite) can identify heavy I/Os against a particular device or chunk. This information can be used to determine where hotspots exist across the system.