Monitor threads with onstat –u output

Use the onstat –u command to display information about active threads that require a database server task-control block.

Active threads include threads that belong to user sessions, as well as some that correspond to database server daemons (for example, page cleaners). Figure 1 shows an example of onstat -u output.

Also use the onstat -u command to determine if a user is waiting for a resource or holding too many locks, or to get an idea of how much I/O the user has performed.

The utility output displays the following information:
  • The address of each thread
  • Flags that indicate the present state of the thread (for example, waiting for a buffer or waiting for a checkpoint), whether the thread is the primary thread for a session, and what type of thread it is (for example, user thread, daemon thread, and so on)

    For information on these flags, see the IBM® Informix® Administrator's Reference.

  • The session ID and user login ID for the session to which the thread belongs

    A session ID of 0 indicates a daemon thread.

  • Whether the thread is waiting for a specific resource and the address of that resource
  • The number of locks that the thread is holding
  • The number of read calls and the number of write calls that the thread has executed
  • The maximum number of current, active user threads
If you execute onstat -u while the database server is performing fast recovery, several database server threads might appear in the display.
Figure 1. onstat -u output
Userthreads
address  flags   sessid   user     tty      wait     tout locks nreads   nwrites
80eb8c   ---P--D 0        informix -        0        0    0     33       19
80ef18   ---P--F 0        informix -        0        0    0     0        0
80f2a4   ---P--B 3        informix -        0        0    0     0        0
80f630   ---P--D 0        informix -        0        0    0     0        0
80fd48   ---P--- 45       chrisw   ttyp3    0        0    1     573      237
810460   ------- 10       chrisw   ttyp2    0        0    1     1        0
810b78   ---PR-- 42       chrisw   ttyp3    0        0    1     595      243
810f04   Y------ 10       chrisw   ttyp2    beacf8   0    1     1        0
811290   ---P--- 47       chrisw   ttyp3    0        0    2     585      235
81161c   ---PR-- 46       chrisw   ttyp3    0        0    1     571      239
8119a8   Y------ 10       chrisw   ttyp2    a8a944   0    1     1        0
81244c   ---P--- 43       chrisw   ttyp3    0        0    2     588      230
8127d8   ----R-- 10       chrisw   ttyp2    0        0    1     1        0
812b64   ---P--- 10       chrisw   ttyp2    0        0    1     20       0
812ef0   ---PR-- 44       chrisw   ttyp3    0        0    1     587      227
 15 active, 20 total, 17 maximum concurrent

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