This FAQ addresses frequently asked questions relating to high availability features of Oracle9i Application Server (Oracle9iAS) Release 2.

Oracle9iAS Release 2 introduces several new mechanisms for high availability, making it a compelling choice for applications that require high availability. This FAQ is broken into the following sections:

• Application High Availability

• Middle Tier High Availability

• Infrastructure Failover

• Oracle9iAS Backup & Recovery

Application High Availability

1. What options does Oracle provide for Application Failover in the J2EE container, OC4J?
   Oracle9iAS's J2EE container, OC4J provides two high performance mechanisms to transparently share state with other servers: (1) Session state replication, which is supported for both EJB sessions and Servlet (or JSP) Sessions, and (2) Java Object Cache, which supports replication and persistence of any Java Object. In order to implement either of these solutions, Oracle9iAS provides a simple, GUI, wizard driven way to cluster OC4J instances across multiple machines.
   

2. Where can I get more information about OC4J?
   See /tech/java/oc4j/index.html. Also see the OC4J documentation at http://download.oracle.com/docs/cd/A97688_07/index.htm and Java Object Cache documentation at: http://download.oracle.com/docs/cd/A97688_07/generic.903/q20223/index.html.

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Middle Tier High Availability

3. What options does Oracle provide for middle tier failover of OC4J applications?
   Multi-node clustering of the middle tier is a key feature of Oracle9iAS. Middle tier clustering can be set up very easily using Wizard based configuration. In a multi-node cluster, if one node goes down, all requests get automatically and transparently re-routed to another node that is up and running.

4. I'd like to test this out. Do you have a set of "how-tos"?
   Yes. See here: /sample_code/products/ias/htdocs/demo/index.html. You can also download this here: /sample_code/products/ias/htdocs/demo/Demo.zip.

5. What Middle Tier install types can be clustered?
   Only multiple installs of "J2EE & Web Cache" can be clustered using Oracle9iAS Clustering.
   

6. Is there any way to cluster the OC4J instances in a "Portal & Wireless" or "BI & Forms" install types?
   Yes, see: /products/ias/ohs/collateral/r2/mod_oc4j_wp.pdf. However, note that (strictly speaking) this wouldn't be considered "clustering".

7. Is an infrastructure repository always required for J2EE & Web Cache clustering ?
   The default clustering mechanism that also provides better configuration management does require the repository.
   However, such a clusters can also be configured manually - see /products/ias/ohs/collateral/r2/mod_oc4j_wp.pdf. In this case, multiple instances are "clustered" using manual configuration and mod_oc4j routes to all of them appropriately.
   Note: There is no way to setup clustering across farms with different repositories. It is feasible to cluster instances within the same farm, even when these instances are not of the install type "J2EE and Web Cache". [See question above.]

8. Does this type of clustering automatically provide for fault tolerance or better availability?
   Yes and No. This kind of setup just provides an automated way to make configuration identical across the instances. For stateless (no state on the server) and state-safe (state saved in a persistent store) applications, this is sufficient (in conjunction with a hardware load balancer or web cache as a front-end).
   However such a setup is not sufficient for stateful application failover, and islands have to be defined. For more information on this, please see the Oracle9iAS documentation.

9. Does Oracle9iAS support Web Cache clusters?
   Yes. To learn more about this, visit the Web Cache page on OTN: /products/ias/web_cache/index.html.

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Infrastructure High Availability

10. What solutions are available for making the Infrastructure Highly Available?
    Oracle has certified several Cold Failover Clustering solutions. Details can be found here: /products/ias/hi_av/index.html.

11. Can Infrastructure be installed on Cold Failover Clusters using HP-Tru64 CAA or IBM-AIX HACMP. ?
    No, these platforms do not support running Infrastructure on CFC. Oracle will provide support for these platforms in the next release.

12. What about Windows FailSafe? Is that supported?
    No, not yet. Oracle will provide Windows Cold Failover Cluster solutions in the next release.

13. Can I use Veritas Clusters?
    Yes, VCS is supported on Solaris.

14. Can the middle tier be installed in a Cold Failover Cluster?
    No. The cold failover cluster solutions are applicable only to the Infrastructure. Due to certain limitations, middle tier Cold Failover Clusters are not possible in version 9.0.2. However, middle tiers can be installed on clustered nodes as long as they are installed on local disks and are not expected to participate in failover. See Hardware Clusters whitepaper on OTN for details: /products/ias/hi_av/index.html.
    

15. Can Infrastructure be RAC enabled?
    In Oracle9iAS (9.0.2 and 9.0.3) RAC is only supported on the customer (back-end) database (with some restrictions as outlined here: /software/products/ias/files/ha-certification.html). Infrastructure cannot be installed in a RAC environment. This will be supported in a future release.

16. Can Infrastructure use DataGuard for high availability?
    Not in version 9.0.2. Again, this will be supported in a future release.

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Oracle9iAS Backup and Recovery

17. How can I backup and recover Oracle9iAS?
    A scripted tool and whitepaper on OTN describe how to perform full backup, incremental backup and subsequent recovery. You can find this document here: /products/ias/hi_av/index.html.

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