AIX LPAR missing hdisk after vios reboot SOLVED

In case that you are doing routine checkup of your LPAR's on IBM pSeries, you probably are checking status of your LPAR OS disks or volume group from time to time.
To check status of your volume group hdisks use this

root@aix-server> [/]  lsvg -p roottvg
rootvg:
PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION
hdisk0                   missing                    546               4                 00..00..00..00..04
hdisk1                   active                       546               0                 00..00..00..00..00
 
As you can see one of hdisk is missing! And you start to panic! "OMG, hdisk is missing, where, how, when?!?!"

There is no place for panic. You will see that one of your disks is missing only after you have restarted one of your VIOS. In are case there is two VIOS. hdisk0 is from first VIOS, hdisk1 is from second VIOS. These two hdisk is creating volume group called rootvg.

How to fix this missing hdisk state?
All you need to do is to activate.  

root@aix-server> [/] varyon rootvg

This will activate your volume group rootvg. After this you will see both of your hdisk as active!
Why this is important? Because of this:

When a volume group is activated, physical partitions are synchronized if they are not current.

But there is one case when you can't make your hdisk active without making additional changes! In this case, after you execute varyon command, error will be prompted and you won't be able to make your hdisk active!

root@aix-server> [/] varyon rootvg
varyonvg: Cannot varyon volume group with an active dump device on a missing physical volume. Use sysdumpdev to temporarily replace the dump device with /dev/sysdumpnull and try again.

So, as error said active dump device is on missing physical volume hdisk0.(I will not explaind here what system dump device is) How to change this? First we will list status of sysdump devices.

root@aix-server> [/]  sysdumpdev -l
primary              /dev/lg_dumplv
secondary            /dev/sysdumpnull
copy directory       /var/adm/ras
forced copy flag     TRUE
always allow dump    FALSE
dump compression     ON






From here we can see, that primary device is located on /dev/lg_dumplv and secondary device is /dev/sysdumpnull. In error message, active dump device is actually primary dump device in sysdumpdev -l. So we need to change that.

root@aix-server> [/] sysdumpdev -p /dev/sysdupmnull

List again sysdump devices.

root@aix-server> [/]  sysdumpdev -l
primary             /dev/sysdumpnullsecondary            /dev/sysdumpnull
copy directory       /var/adm/ras
forced copy flag     TRUE
always allow dump    FALSE
dump compression     ON

Now execute activation of volume group.


root@aix-server> [/] varyon rootvg

root@aix-server> [/] 
root@aix-server> [/]  lsvg -p rootvg
rootvg:
PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION
hdisk0                         active            546                    4             00..00..00..00..04
hdisk1                         active            546                    0             00..00..00..00..00

As you can see now, both hdisk are active now.
Now, change back you primary dump device

root@aix-server> [/] sysdumpdev -p /dev/lg_dumplv