Sunday, November 17, 2013

DLPAR not doing it for you anymore?

Based on my experience, the most common issue that prevents DLPAR operations from working are network problems. Before diving into the deep end and trying to debug RSCT, it’s always best to start with the basics. For example, can you ping the HMC from the LPAR? Can you ping the LPAR from the HMC? If either of these tests fails, check the network configuration on both components before doing anything else.

On the HMC check the network settings first e.g.

Click on HMC Configuration and then Customize Network Settings.

– Verify the IP address, netmask, default gateway, network routes, DNS server are all set correctly.

– Check the LPAR communications box in HMC configuration screen for LAN adapter that is used for HMC-to-LPAR communication.

– By the way, unlike POWER4 systems, LPARs on POWER5 and POWER6 systems do not depend on host name resolution for DLPAR operations.

Check routing on the LPAR and the HMC.

– Use ping and the HMC’s Test Network Connectivity task to verify the LPAR and the HMC can communicate with each other.

If you check the network and you are happy that the LPAR and the HMC can communicate, then perhaps you need to re-initialise the RMC subsystems on the AIX LPAR. Run the following commands:

# /usr/sbin/rsct/bin/rmcctrl –z
# /usr/sbin/rsct/bin/rmcctrl –A
# /usr/sbin/rsct/bin/rmcctrl –p

Wait up to 5 minutes before trying DLPAR again. If DLPAR still doesn’t work i.e. the HMC is still reporting no values for DCaps, and the IBM.DRM subsystem still won’t start, try using the recfgct command.

 hscroot@hmc1:~> lspartition -dlpar


<#5> LPAR:<24"">

       Active:<1>, OS:, DCaps:<0x0>, CmdCaps:<0x0 0x0="">, PinnedMem:<768>


 # /usr/sbin/rsct/install/bin/recfgct

Wait 5 minutes. This should resolve your DLPAR issue. The IBM.DRM subsystem should now be active and there should be good (non-zero) values for DCaps:

# lssrc -g rsct_rm

Subsystem         Group            PID          Status
 IBM.DRM          rsct_rm          6881300      active
 IBM.CSMAgentRM   rsct_rm          7274530      active
 IBM.ServiceRM    rsct_rm          6029480      active
 IBM.AuditRM      rsct_rm          6357058      active
 IBM.ERRM         rsct_rm          4456566      active
 IBM.LPRM         rsct_rm          6946986      active

hscroot@hmc1:~> lspartition -dlpar


<#5> LPAR:<24"">

       Active:<1>, OS:, DCaps:<0xc5f>, CmdCaps:<0x1b 0x1b="">, PinnedMem:<994>


 Only run the rmcctrl and recfgct commands if you believe something has become corrupt in the RMC configuration of the LPAR. The fastest way to fix a broken configuration or to clear out the RMC ACL files after cloning (via alt_disk migration) is to use the recfgct command.

 These daemons should work “out of the box” and are not typically the cause of DLPAR issues. However, you can try stopping and starting the daemons when troubleshooting DLPAR issues.

 The rmcctrl -z command just stops the daemons. The rmcctrl -A command ensures that the subsystem group (rsct) and the subsystem (ctrmc) objects are added to the SRC, and an appropriate entry added to the end of /etc/inittab and it starts the daemons.

 The rmcctrl –p command enables the daemons for remote client connections i.e. from the HMC to the LPAR and vice versa.

If you are familiar with the System Resource Controller (SRC) you might be tempted to use stopsrc and startsrc commands to stop and start these daemons.

Do not do it; use the rmcctrl commands instead.

 If /var is 100% full, use chfs to expand it. If there is no more space available, examine subdirectories and remove unnecessary files (for example, trace.*, core, and so forth). If /var is full, RMC subsystems may fail to function correctly.

The polling interval for the RMC daemons on the LPAR to check with the HMC daemons is 5-7 minutes; so you need to wait long enough for the daemons to start up and synchronize.

The Resource Monitoring and Control (RMC) daemons are part of the Reliable, Scalable Cluster Technology (RSCT) and are controlled by the System Resource Controller (SRC). These daemons run in all LPARs and communicate with equivalent RMC daemons running on the HMC. The daemons start automatically when the operating system starts and synchronize with the HMC RMC daemons.

The daemons in the LPARs and the daemons on the HMC must be able to communicate over the network for DLPAR operations to succeed. This is not the network connection between the managed system (FSP) and the HMC; it is the network connection between the operating system (AIX) in each LPAR and the HMC.

Note: Apart from rebooting, there is no way to stop and start the RMC daemons on the HMC.

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