Working With Device Settings

Audience: Administrators

Date: November 22, 2003

Here are a few commands for working with devices on an AIX system.

To list all devices on an AIX system, run the command

# lsdev -C

To list specific device types, use the "-Cc" flag. For example, this command lists only adapters.

# lsdev -Cc adapter

To list the attributes of a particular device

# lsattr -HEl <device>

e.g.:

# lsattr -HEl hdisk1
attribute       value                            description                 user_settable

pvid            000008767ae0ba390000000000000000 Physical volume identifier  False
queue_depth     3                                Queue depth                 True
write_queue_mod 0                                Write queue depth modifier  True
adapter_a       ssa0                             Adapter connection          False
adapter_b       none                             Adapter connection          False
primary_adapter adapter_a                        Primary adapter             True
reserve_lock    yes                              RESERVE device on open      True
connwhere_shad  0004AC504D6500D                  SSA Connection Location     False
max_coalesce    0x20000                          Maximum coalesced operation True
size_in_mb      2255                             Size in Megabytes           False
location                                         Location Label              True

The attributes which you can change have a "True" value under the "user_settable" column.

To display the legal values for an attribute.

# lsattr -Rl <device> -a <attribute>

# lsattr -Rl hdisk1 -a queue_depth 0...200 (+1)

In this case, the queue_depth can be set from 0 to 200 in increments of 1. See the AIX documentation for more information on the meaning of each attribute

To change an attribute, use the "chdev" command. Normally you can not change an attribute of a device that is on-line. The following command changes the attribute in the ODM, and goes into affect after a reboot (or rmdev/mkdev).

# chdev -l <device> -a <attribute>=<new value> -P

To change an attribute of a device that is offline:

# chdev -l <device> -a <attribute>=<new value>

Thanks to Dan Braden for this tip.