There isn't any failover capability in ArcSDE (as that seven year old PDF correctly states). Oracle's high availability enviroment is managed by RAC (Real Application Cluster). Install/ config of RAC is outside the scope of the ArcGIS forums, but the generic description is correct -- there are two (or more) servers accessing one external disk store, which is stored in common for active/passive or active/active use. Oracle also has a feature called Data Guard, which permits log shipping from a primary database to have active/passive or active/active databases with two (or more) disk stores. More exotic forms can include Data Guarding RAC nodes (many servers, many disk stores). Since that whitepaper was released, ArcGIS has introduced its own replication capability, which is captured at the ArcGIS level and doesn't use ArcSDE (beyond versioning). - V
Hello, I have worked in setting up a High Availability environment where oracle and arcsde are configured on Microsoft Failover Cluster Manager and Oracle Failsafe. ArcSDE is configured as a generic service and with the failover it resumes on same database instance on another server with NAS architecture. So, I hope it answers your question if you are asking that it is the same single ArcSDE instance for both oracle servers.
In my case data is located on SAN, where as Oracle 11g R2 64 bits is on another physical machine, now presently I have an ArcSDE machine connected with geodatabase in service mode, what I want to do is Have another ArcSDE machine which should have a service to provide connection to same geodatabase in case of any failure of 1st ArcSDE machine using same oracle server.
Well, it is doable. First you need to do to setup Microsoft Failover Cluster Manager and setup a virtual host in it. Then you need to install Oracle database, Oracle Failsafe and ArcSDE on both node machines which you want to be acting as failover nodes (don't execute the post installation for ArcSDE at this point). Then You setup the oracle database instance against which you need to run ArcSDE (Run post installation for ArcSDE here). Now you do the configuration for the other node specifically to share database instance and ArcSDE service. You can test the failover from the Microsoft Failover Cluster Manager.
Adding more ArcSDE servers only adds additional single points of failure (reducing reliability). Instead, use Direct Connect to connect tot the RAC node directly, and remove the application server from the equation. Each session that was active when the Oracle instance fails over would need to be restarted (and restarted again when the primary returns), but that would be the case with multiple ArcSDE servers anyway. - V
I worked on a project where we had to evaluate the relative performance of a cluster of VMs in a similar configuration with a single equivalent physical server. The exact details were under non-disclosure, but we found that a physical server out-performed a cluster of SOCs running on the same host as VMs, generating 40-120% more maps per minute over a 10+ minute test period. The details in our test report were sufficiently glaring that there was no objection when we requested variance from the "all systems shall be VMs" facility configuration requirement. We made use of dozens of VMs on that project, but not where production use of ArcGIS Server or ArcSDE was involved. - V