Service group Dependency FAQ

[Veritas_Veritas]

Hi Friends,

I have one Doubt while reading User guide fo vcs4.1.

It says ,Soft dependency provides the following enhanced flexibility:

When both groups are online, the child group can be taken offline while the parent is online and vice versa (the parent group can be taken offline while the child is online).

But in FAQ's section of online local, it says

Can child group be taken offline when parent group is online? Firm=No Soft=No.

isn't it should be Firm=No and Soft=yes.

Please suggest.

Thanks in Advance,

Munish

[Gene_Henriksen]

You should find that if you attempt to offline the child SG while the parent SG is online that you will get a dependency violation and not be allowed to do this.

Soft means if child goes offline due to fault, parent stays online.
Firm means if child goes offline due to fault, parent goes offline and comes back online after child is online
With soft and firm, if the parent goes offline, then the child SG is not disturbed. If you want them to come back online, you need to use triggers such as postoffline.

Hard locks the two SGs together so that if either go offline, the other also goes offline, then the come back online in the correct order. This is only available in the  Online Local relationship.

[Veritas_Veritas]

Hi Gene,

Thanks you so much....

You are the best.

Iam still trying to understand SG's dependencies which I think are difficult to understand from all perspectives.:-)

Cheers!!

Munish

[Gene_Henriksen]

Students often have trouble in class with these also.

Take this example: SQL must come up and then you can bring up an application that uses SQL. They must run on the same system.

Since SQL must come up first, it is the child, App is the parent. The relationship is "online".
They must be on the same system so the next part of the relationship is "local", now we have "online local"
The must failover together is one fails, so they will be on the same system, so we use "hard", now we have the full relationship: online local hard.

Another: Sql must come online then the web app can come online anywhere in the cluster.

SQL must be online first, then the app so SQL is child and we have an "online"
Web can come up anywhere in cluster, so the next part is "global": "online global".

Now, if sql fails and fails over to another machine, must web come down and up to re-connect with sql?
If the answer is yes, then the relationship is "firm", if web must not be "bounced" after sql fails over, then the relationship is "soft".

Online global soft
online global firm

The offline relationship is the case where you never want development running on the same system as production. So the relationship has prod as child, then dev must come up elsewhere in the cluster.
Offline remote

In cases where the rules would be broken if the parent were to come up on a remaining system, the parent cannot come up.

[Veritas_Veritas]

Brillant gene...