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onstat -g ioq Disk IO Statistics by Queue

The onstat -g ioq command provides statistics on the disk I/O by queue. The command line can specify the queue name

AIO I/O queues:                                                 
q name/id    len maxlen totalops  dskread dskwrite  dskcopy     
drda_dbg   0      0      0        0        0        0        0
sqli_dbg   0      0      0        0        0        0        0
  kio   0      0     32    28354    12980    15374        0     
  adt   0      0      0        0        0        0        0     
  msc   0      0      1     3169        0        0        0     
  aio   0      0      1       95        9        2        0     
  pio   0      0      0        0        0        0        0     
  lio   0      0      0        0        0        0        0     
  gfd   3      0      0        0        0        0        0     

Output Description

Heading Description Format
q name The AIO queue name.
  • drda_dbg: Handles I/O for DRDA feature
  • sqli_dbg: Handles I/O for SQL Interface Debugging feature
  • fifo: Handles I/O for FIFO VPs
  • adt: Handles auditing I/O
  • msc: Handles miscellaneous I/O
  • aio: Handles asynchronous I/O
  • kio: Handles kernel AIO
  • pio: Handles physical logging I/O
  • lio: Handles logical logging I/O
  • gfd: Global File Descriptor - Each primary and mirror chunk is given a separate global file descriptor. Individual gfd queues are used depending on whether kaio is on and the associated chunk is cooked or raw.
q id The global file descriptor associated with this queue (files only). Dec
len The current number of active requests in this queue. Dec
maxlen The maximum number of requests this queue has held. Dec
totalops The total number of operations performed for this queue. Dec
dskread The total number of read operations performed for this queue. Dec
dskwrite The total number of write operations performed for this queue. Dec
dskcopy The total number of copy operations performed for mirroring against this queue. Dec


    One gfd queue name exists for each chunk in the system.

Monitoring and Tuning

    The information from the onstat -g ioq command can assist in identifying bottlenecks with the processing of I/O through the queues. If the maxlen column for the AIO queue tends to exceed 25, additional AIO VPs should be started.

    The onstat -g ioq output for the global file descriptors (gfd) or chunks may also identify a potential I/O problem with specific disks in the system if certain gfd queues begin to back up. It may also point out a chunk that contains a table that needs better partitioning (fragmentation).

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