lvmo Command

Purpose

Manages lvm pbuf tunable parameters.

Syntax

lvmo -v Name -o Tunable [ =NewValue ]

lvmo -a [ -v vgname ]

lvmo -L [ Tunable ]

Description

The lvmo command sets or displays pbuf tuning parameters. The equal sign can be used to set a particular tunable to a given value. Otherwise, if no equal sign is used, the value of the tunable will be displayed.

Attention: Misuse of the lvmo command can cause performance degradation or operating-system failure.
The lvmo -a command generates pbuf and blocked I/O statistics. The pbuf and blocked I/O report has the following label:
Label Description
vgname Volume group name specified with the -v option.
pv_pbuf_count The number of pbufs that are added when a physical volume is added to the volume group.
total_vg_pbufs Current total number of pbufs available for the volume group.
max_vg_pbuf_count The maximum number of pbufs that can be allocated for the volume group.
pervg_blocked_io_count Number of I/O's that were blocked due to lack of free pbufs for the volume group.
pv_min_pbuf The minimum number of pbufs that are added when a physical volume is added to any volume group.
global_blocked_io_count Number of I/O's that were blocked due to lack of free pbufs for all volume groups.
aio_cache_pbuf_count Current total number of pbufs available for aio_cache logical volume in the volume group.

Flags

Item Description
-a Displays value for all tunable parameters, one per line in pairs tunable = value.
-o Tunable [=NewValue ] Displays the value or sets Tunable to NewValue.
-L [ Tunable ] Lists the characteristics of one or all of the tunables, one per line, using the following format: 
NAME                      CUR    DEF    BOOT   MIN    MAX    UNIT   TYPE 
     DEPENDENCIES 
-------------------------------------------------------------------------
global_blocked_io_count    0      0     n/a     0      0             S 
     pervg_blocked_io_count 
-------------------------------------------------------------------------
max_vg_pbufs              16384  n/a    n/a   16384    none          S 
     max_vg_pbuf_count 
     pv_min_pbuf
     pv_pbuf_count
     total_vg_pbufs
-------------------------------------------------------------------------
max_vg_pbuf_count          0      0      n/a    0      none          M 
     max_vg_pbufs
     pv_min_pbuf
     pv_pbuf_count
     total_vg_pbufs
-------------------------------------------------------------------------
pervg_blocked_io_count     0      0      n/a    0      0             S
     global_blocked_io_count
------------------------------------------------------------------------- 
pv_min_pbuf               512    512     n/a    0      none          D
     max_vg_pbufs
     max_vg_pbuf_count
     pv_pbuf_count
     total_vg_pbufs
-------------------------------------------------------------------------
pv_pbuf_count             512    512    n/a     1      16384         D
     max_vg_pbufs
     max_vg_pbuf_count
     pv_min_pbuf
     total_vg_pbufs
-------------------------------------------------------------------------
total_vg_pbufs            512    n/a    n/a     0      0             S
     max_vg_pbufs
     max_vg_pbuf_count
     pv_min_pbuf
     pv_pbuf_count
-------------------------------------------------------------------------
... 
where: 
    n/a means parameter not supported by the current platform or kernel
Parameter types:
    S = Static: cannot be changed
    D = Dynamic: can be freely changed
    B = Bosboot: can only be changed using bosboot and reboot
    R = Reboot: can only be changed during reboot
    C = Connect: changes are only effective for future socket connections
    M = Mount: changes are only effective for future mountings
    I = Incremental: can only be incremented
    d = deprecated: deprecated and cannot be changed
Value conventions:
    K = Kilo: 2^10       G = Giga: 2^30       P = Peta: 2^50      
    M = Mega: 2^20       T = Tera: 2^40       E = Exa: 2^60

Tunable Parameters

Item Description
pv_pbuf_count The number of pbufs that is added when a physical volume is added to the volume group.
max_vg_pbuf_count The maximum number of pbufs that can be allocated for the volume group. Note: The volume group must be varied off and varied on again for this value to take effect. This value does not affect rootvg.
pv_min_pbuf The minimum number of pbufs that is added when a physical volume is added to any volume group. Note: Use the ioo command to change this value.
aio_cache_pbuf_count The total number of pbufs that is allocated for aio_cache logical volume in the volume group.
workQ_size The size of the hash table that is used to track I/O requests for logical volumes in the volume group.

Exit Status

This command returns zero for successful completion; otherwise it returns nonzero.

Security

You must have root authority to run this command.

Attention RBAC users and Trusted AIX users: This command can perform privileged operations. Only privileged users can run privileged operations. For more information about authorizations and privileges, see Privileged Command Database in Security. For a list of privileges and the authorizations associated with this command, see the lssecattr command or the getcmdattr subcommand.

Examples

  1. To display the value for the pv_pbuf_count, type the following: 
    lvmo -v rootvg -o pv_pbuf_count
  2. To set the pv_pbuf_count value to 2048, type the following: 
    lvmo -v rootvg -o pv_pbuf_count=2048
  3. To generate pbuf and blocked I/O statistics, type the following: 
    lvmo -a

Location

/usr/sbin/lvmo