1) You can use Oracle GI to cluster applications. From a non-database perspective I guess you could argue it's not as mature as Sun Cluster or Veritas Cluster but in principle it can be used to cluster applications although I personally have never used it for anything other than databases.
2) I suppose in simple terms a database can be considered just an application like any other. Oracle GI is a requirement to cluster a database and provides the HA services for the database. RAC is what a clustered database is called and is an additional license requirement for clustered databases.
3) No...OracleGI is required to cluster 11g databases. You may also use an additional clusterware such as Sun Cluster but would need to identify what this would give you that GI can't. On Oracle 9i we would have Oracle RAC's using just Sun Cluster or HACMP on AIX which would do the clustering aspect, but that changed with 10g when CRS was intoruced and for 11g we have GI .
4) I haven't a clue !! Might have to ask Larry and his marketing bods about the thinking behind it !!
5) Oracle GI is a requirement for a RAC database. As per point 3 above you may use additional clustering but you would need to identify what it would give you that Oracle GI wouldn't. For example we used a 10g RAC database on AIX using raw devices (with archivelogs on file systems) and we used CRS to cluster the vips, listener etc and used HACMP to cluster the volume groups and filesystems which held the datafiles and archivelogs. The raw devices were used due to vendor having only certified it to run on raw devices so ASM wasn't an option. For 11g raw devies are no longer required but you can use supported filesystems for which you might want to use for example Veritas Cluster, but again what would Veritas Cluster give you that GI wouldn't.
So 3rd party clustering was only allowed for RAC prior to 10g ? When Oracle Clusterware was introduced at 10g this became the madatory clusterware for RAC ?
In 3) you say you could use additional clusterware - but what would you use it for if RAC mandates / requires Oracle Clusterware ? Are you saying you could use it for storage clustering as a means to make the storage shareable for the Database Cluster ?
In 5) am I right in assumiong that you used RAC & Oracle GI to cluster your Database Server ( database instances ) but you used HACMP to cluster your storage ( thereby in effect making the storage shareable between the nodes i.e. facilitating the shared storage required for the Database cluster ) ?
You said raw devices were used due to the vendor having only certified it ... Which Vendor ( application, OS ? ) and certified what ( database ? ) - seems strange for something to only be certified on raw devices !
Yes, with 10g you had to use CRS, and with 11g you have to use GI. For 9i RAC you would use Sun Cluster or Verits Cluster or whatever.
For 11g RAC you need GI. As above, you may use additional clusterware if you deem it neccessary. I gave the example above where for a 10g RAC we used CRS to cluster the database/listener/vip and used HACMP to cluster the filesystems and volume groups. The filesystems were not shared but would fail over to another node in the event of node failure, which was handled by HACMP. The volume groups whch contained the raw devices were shared volume groups. For 11g I have never used additional clusterware on top of CRS and have always used ASM which is part of GI.
The application vendor only certified the database to run on 10g on AIX with raw devices. What's strange about that? It might be unusual as you would probably expect them to use ASM instead of raw devices but it is what it is.
See the following Oracle Note for further information : Using Oracle Clusterware with Vendor Clusterware FAQ (Doc ID 332257.1)
This might be easier to explain if you can explain what problem you are trying to solve?
I am just trying to get my head around what if any 3rd party server clusterware Oracle RAC can use and under what circumstances / conditions.
Q1. Are you saying that from 10g onwards, Oracle Clusterware / Grid Infrastructure is the ONLY clusterware that RAC can use or rather is it simply Oracle's preferred clusterware for RAC ? From below, it looks as if Oracle Clusterware is NOT the only Clusterware that RAC can use
From the note you quoted it looks as if 3rd party clusterware can indeed be used with RAC. It states Oracle Clusterware can be integrated with vendor clusterware - Oracle Clusterware itselfs deals with the integration as part of the installation process of Oracle Clusterware / GI in an environment that is already configured for a 3rd party / vendor specific cluster.
Also I know Sun Clusters explicitly states that it can be used with Oracle RAC.
Q2. So whilst it appears as if RAC can use 3rd party clusterware, what I am not sure about is, if that is the case does RAC still require Oracle Clusterware / GI and then that in turn integrates with 3rd party clusterware ? In effect RAC sits on top of Oracle Clusterware which would in turn sit on top of the 3rd party clustering solution ?
Q3. If from Q2. Oracle Clusterware is still needed even when 3rd party clusterware is involved - it begs the question why not simply use Oracle Clusterware on its own ? The only reason Ican think of is if you were forced into using hardware for your RAC that had already been configured for a 3rd party cluster ( for other applications ) and you had no other choice of hardware to use for your RAC.
You can use other 3rd party clusterware products. However, for newer Oracle versions you are required to use Oracle's clusterware. Oracle RAC will communicate only with Oracle's clusterware. If a 3rd party clusterware is in use, then Oracle's clusterware just becomes a pass-through between RAC and the 3rd party clusterware software.