SHOW CLUSTER shows different parameter values compared to F$GETSYI and SYSMAN

[Jeremy Begg]

Hi,

Today one of my (highly experienced) users was explaining VMSclusters to a new employee.

Things were going well until he noticed SHOW CLUSTER reported different values for EXPECTED_VOTES and QUORUM on both systems: it shows EXPECTED_VOTES=1 on node METMAX and 3 on node METMIN, and QUORUM=1 on METMAX and 2 on METMIN.  (See attachment for details.)

My user alerted me to this and rightly queried the cluster setup.  So I looked a bit closer and saw that SHOW CLUSTER disagrees with F$GETSYI and SYSMAN:

On METMAX ...

METMAX> write sys$output f$getsyi("EXPECTED_VOTES")
3
METMAX> mcr sysman
SYSMAN> param use active
SYSMAN> param show expected_votes
Node METMAX:   Parameters in use: ACTIVE
Parameter Name            Current    Default    Minimum    Maximum Unit  Dynamic
--------------            -------    -------    -------    ------- ----  -------
EXPECTED_VOTES                  3          1          1        127 Votes

SYSMAN> param use current
SYSMAN> param show expected_votes
Node METMAX:   Parameters in use: CURRENT
Parameter Name            Current    Default    Minimum    Maximum Unit  Dynamic
--------------            -------    -------    -------    ------- ----  -------
EXPECTED_VOTES                  3          1          1        127 Votes

SYSMAN> exit
METMAX> search sys$system:modparams.dat votes
VOTES=1
EXPECTED_VOTES=3
QDSKVOTES=1
METMAX>

 On METMIN:

METMIN> write sys$output f$getsyi("EXPECTED_VOTES")
3
METMIN> mcr sysman
SYSMAN> param use active
SYSMAN> param show expected_votes
Node METMIN:   Parameters in use: ACTIVE
Parameter Name            Current    Default    Minimum    Maximum Unit  Dynamic
--------------            -------    -------    -------    ------- ----  -------
EXPECTED_VOTES                  3          1          1        127 Votes

SYSMAN> param use current
SYSMAN> param show expected_votes
Node METMIN:   Parameters in use: CURRENT
Parameter Name            Current    Default    Minimum    Maximum Unit  Dynamic
--------------            -------    -------    -------    ------- ----  -------
EXPECTED_VOTES                  3          1          1        127 Votes

SYSMAN> exit
METMIN> search sys$system:modparams.dat votes
VOTES=1
EXPECTED_VOTES=3
QDSKVOTES=1
METMIN>

So what's going on?  How can SHOW CLUSTER be showing such different values for METMAX?

Thanks,

Jeremy Begg

[Volker Halle]

Jeremy,

please also check with SDA> SHOW CLUSTER on both nodes, what the CSB (Cluster System Block) data contains for the nodes in the cluster.

The SHOW CLUSTER utility may not be using F$GETSYI.

Volker.

[Hoff]

Somebody has probably been using SET CLUSTER/EXPECTED_VOTES over the lifetime of this cluster, either explicitly or during a shutdown.    You can issue the command (sans value) and reset the values.

[Jeremy Begg]

Yes, SDA> SHOW CLUSTER shows the same values as the SHOW CLUSTER command.

I tried SET CLUSTER/EXPECTED_VOTES with and without a value (3) but it appears to have no effect:

SHOW CLUSTER output before:

│ METMAX │ VMS V8.4 │ 1 │ 1 │ 1 │ MEMBER │

│ METMIN  │ VMS V8.4 │ 1 │ 3 │ 2 │ MEMBER │

(The three numbers are VOTES, EXPECTED_VOTES and QUORUM.)

Then

METMAX> set cluster/expect
%SET-I-EXPTD_VOTES, new value of expected votes is 3, yields quorum of 2

METMAX> show cluster

│ METMAX │ VMS V8.4 │ 1 │ 1 │ 1 │ MEMBER │

│ METMIN  │ VMS V8.4 │ 1 │ 3 │ 2 │ MEMBER │

and SDA agrees that the EXPECTED_VOTES has not changed.

Thanks

[Hoff]

...and SDA agrees that the EXPECTED_VOTES has not changed...

Has the quorum value changed?  EXPECTED_VOTES relates to the boot environment, and is not relevant to OpenVMS operations once cluster connections have been established and the value of quorum initially derived from the parameter EXPECTED_VOTES has been verified as being available.  

Once cluster connections have been established and the initial boot-time quorum hang has been cleared, the total number of votes actually present in the configuration are used to calculate the quorum value, and it is the quorum value which is the only value here that matters.  

The SET CLUSTER /EXPECTED_VOTES command centrally effects the current quorum value, and not the value of EXPECTED_VOTES.

ps:  searching the sys$system:modparams.dat file can be slightly hazardous with recent releases, as that file can now include other files with parameter settings.

[Jeremy Begg]

SET CLUSTER/EXPECTED_VOTES did not appear to have any effect.

Both EXPECTED_VOTES and QUORUM were unchanged.

Thanks