14
Real Application Cluster (RAC)

This chapter describes what is BS2000 specific for RAC. Parts of this chapter are:

• BS2000 prerequisites for RAC

• Installation of RAC

• Creation and Configuration of an RAC

• Restrictions

For more information see Oracle9i Real Application Clusters (a complex of books).

BS2000 prerequisites for RAC

In order to achieve the capabilities of RAC Oracle needs

• an interprocess communication system between the nodes of a cluster,

• a node monitor (or cluster monitor) and

• a shared file system.

The interprocess communication system enables Oracle to exchange messages and coordinate operations between the instances on the cluster, the node monitor is telling Oracle which node is part of the cluster and which is not (and prohibits 'dead nodes' to interfere with the 'healthy' ones), the shared file system is giving access of the common database files to the instances on the different nodes of the cluster.

This set of functions is delivered on BS2000 by HIPLEX MSCF. You must run HIPLEX MSCF as an XCS ('cross coupled system') network with an XCS shared pubset. RAC cannot operate without these prerequisites.

For more information on HIPLEX MSCF see BS2000/OSD HIPLEX MSCF, BS2000 Processor Networks.

Installation of RAC

Installation of the RAC software is not different from the single instance BS2000 installation. RAC is part of the Oracle9i Release 2 tape (see chapter Installing/Upgrading Oracle Server Software) and is implictely installed when you install Oracle9i.

It is important to install the Oracle software on an XCS shared pubset in order to have shared access from different XCS nodes (i.e. the default pubset of your installation userid should be an XCS pubset).

Oracle9i Real Applications Cluster Setup and Configuration makes a distinction of 4 steps for RAC installation:

1. install operating system dependent clusterware

2. configure shared disks

3. install Oracle9i Enterprise Edition and Real Application Cluster software

4. create and configure your database

With an MSCF XCS cluster and an XCS shared pubset you implicitely got clusterware and shared disks with a cluster file system (as refered to in Oracle9i Real Applications Cluster Setup and Configuration, ch. about Configuring the Shared Disks). This means: we are arrived at the end of step 2.

The usual single instance installation puts us at the end of step 3.

The fourth step is the subject of the next section.

Creation and Configuration of a Database

There is no Database Configuration Assistant on BS2000. You must use the manual creation method (see chapter about "Manually Creating Real Application Cluster Databases" in Oracle9i Real Applications Cluster Setup and Configuration).

In order to avoid RAC process overhead for non-RAC instances on BS2000 an ORAENV parameter is telling Oracle if RAC should be switched on or off:

ENABLE_RAC=TRUE/FALSE 

This parameter controls RAC operation on a BS2000 cluster. It does not replace INIT.ORA parameters like CLUSTER_DATABASE=TRUE etc. The meaning of all RAC related parameters is unchanged. ENABLE_RAC=TRUE in ORAENV must be set as a prerequisite to use RAC on BS2000.

One more ORAENV parameter is important:

ALARM_TIMER_LIMIT 

RAC is relying on timer accuracy which must be much more precise than usually available on BS2000. Therefore a special method to improve timer accuracy has been implemented for RAC. This parameter says: all timer limits below the given value should be handled by this precise method, all limits above by the traditional method.

The type of the value is thousandth of seconds. E.g., ALARM_TIMER_LIMIT=10000 says: below 10 seconds use the precise method, above the traditional method.
ALARM_TIMER_LIMIT=10000 is the recommended setting for RAC on BS2000.

When a cluster node is using a ZAS-LAN interface one more parameter may be helpful. In this case contact your Oracle Customer Support Representative.

In general comments and hints given in the chapter "Manually Creating Real Application Cluster Databases" in Oracle9i Real Applications Cluster Setup and Configuration are valid for BS2000, e.g.

• Setting CREATE DATABASE Options for Cluster-Enabled Environments (MAXINSTANCES, MAXLOGFILES etc.)

• Database Objects to Support Clusters
  (rollback segments, threads, online redo logs etc.)

• Creating a Database Manually

  In this step following differences may be observed:

  • Of course you need not install the Oracle software when it is already installed as we assume in this section.

  • Host name and Node name are not relevant for BS2000.

  • There is no SRVCTL utility and no Global Services Daemon (GSD) on BS2000, however this does not restrict RAC operation. BS2000 does not support at present an 'RAC configuration' and an oratab file.

  • The following tasks
    • Set ORACLE_SID for each node

    • Create the server parameter file

    • Create the password files

    • Prepare a CREATE DATABASE script for the cluster database

    • Create the database

    • Backup the database

    • Configure Oracle Net on all nodes

    • Create RAC's Data Dictionary views with CATCLUST.SQL

    do not differ from the proceeding explained in the chapter "Manually Creating Real Application Cluster Databases" of Oracle9i Real Applications Cluster Setup and Configuration.

Restrictions

On BS2000 there is no

• Database Configuration Assistant

• Server Control Utility

• Real Application Cluster Guard