To set up the OracleAS Disaster Recovery solution to use DNS hostname resolution, site-specific DNS servers must be set up in the production and standby sites in addition to the overall corporate DNS servers (usually more than one DNS server exists in a corporate network for redundancy). Figure 6–3 provides an overview of this setup.
Table 6–3 Logical and virtual hostname entries in each /etc/hosts file of example in
Figure 6–2
Host Entries in /etc/hosts
asmid1 in production site 123.1.2.333 asmid1.oracle.com asmid1 123.1.2.334 asmid2.oracle.com asmid2 123.1.2.111 infra.oracle.com infra asmid2 in production site 123.1.2.334 asmid2.oracle.com asmid2
123.1.2.333 asmid1.oracle.com asmid1 123.1.2.111 infra.oracle.com infra infra in production site 123.1.2.111 infra.oracle.com infra
123.1.2.333 asmid1.oracle.com asmid1 123.1.2.334 asmid2.oracle.com asmid2 asmid1 in standby site 213.2.2.443 asmid1.oracle.com asmid1 213.2.2.444 asmid2.oracle.com asmid2 213.2.2.210 infra.oracle.com infra asmid2 in standby site 213.2.2.444 asmid2.oracle.com asmid2
213.2.2.443 asmid1.oracle.com asmid1 213.2.2.210 infra.oracle.com infra infra in standby site 213.2.2.210 infra.oracle.com infra
213.2.2.443 asmid1.oracle.com asmid1 213.2.2.444 asmid2.oracle.com asmid2
See Also: Appendix A, "Setting Up a DNS Server" for instructions on how to set up a DNS server in a UNIX environment.
Setting Up the OracleAS Disaster Recovery Environment
Figure 6–3 DNS resolution topology overview
For the above topology to work, the following requirements and assumptions are made:
■ The production and standby sites’ DNS servers are not aware of each other. They make non authoritative lookup requests to the overall corporate DNS servers if they fail to resolve any hostnames within their specific sites.
■ The production site and standby site DNS servers contain entries for middle tier physical hostnames and Infrastructure virtual hostnames. Each DNS server contain entries of hostnames within their own site only. The sites have a common domain name that is different from that of the overall corporate domain name. ■ The overall corporate DNS servers contain logical hostname entries for the middle
tier hosts and Infrastructure hosts of both production and standby sites.
■ In UNIX, the /etc/hosts file in each host does not contain any entries for the physical, logical, or virtual hostnames of any host in either site. In Windows, this applies to the file C:\WINDOWS\system32\drivers\etc\hosts.
To set up the OracleAS Disaster Recovery solution for DNS resolution:
1. Configure each of the overall corporate DNS servers with the logical hostnames of all the hosts in the production and standby sites. Using the example in Figure 6–2, the following entries are made:
prodmid1.oracle.com IN A 123.1.2.333 prodmid2.oracle.com IN A 123.1.2.334 prodinfra.oracle.com IN A 123.1.2.111 standbymid1.oracle.com IN A 213.2.2.443 standbymid2.oracle.com IN A 213.2.2.444
Setting Up the OracleAS Disaster Recovery Environment
standbyinfra.oracle.com IN A 213.2.2.210
2. For each site, production and standby, create a unique DNS zone by configuring a DNS server as follows:
a. Select a unique domain name to use for the two sites that is different from the corporate domain name. As an example, let’s use the name "oracleas" for the domain name for the two sites in Figure 6–2. The high level corporate domain name is oracle.com.
b. Configure the DNS server in each site to point to the overall corporate DNS servers for unresolved requests.
c. Populate the DNS servers in each site with the physical hostnames of each middle tier host and the virtual hostname of each Infrastructure host. Include the domain name selected in the previous step.
For the example in Figure 6–2, the entries are as follows: For the production site’s DNS:
asmid1.oracleas IN A 123.1.2.333 asmid2.oracleas IN A 123.1.2.334
infra.oraclas IN A 123.1.2.111
For the standby site’s DNS:
asmid1.oracleas IN A 213.2.2.443 asmid2.oracleas IN A 213.2.2.444
infra.oracleas IN A 213.2.2.210
Additional DNS Server Entries for Oracle Data Guard
Because Oracle Data Guard technology is used to synchronize the production and standby Infrastructure databases, the production Infrastructure must be able to reference the standby Infrastructure and vice versa.
For this to work, the IP address of the standby Infrastructure host must be entered in the production site’s DNS server with a unique hostname with respect to the
production site. Similarly, the IP address of the production Infrastructure host must be entered in the standby site’s DNS server with the same hostname. The reason for these DNS entries is that Oracle Data Guard uses TNS Names to direct requests to the production and standby Infrastructures. Hence, the appropriate entries must be made to the tnsnames.ora file as well.
Using the example in Figure 6–2 and assuming that the selected name for the remote Infrastructure is "remoteinfra", the entries in the DNS server in the production site are:
asmid1.oracleas IN A 123.1.2.333
Note: If you are using the OracleAS Cold Failover Cluster solution for the Infrastructure in either site, enter the cluster’s virtual hostname and virtual IP address. For example, in the previous step above, infra is the virtual hostname and
123.1.2.111 is the virtual IP of the cluster in the production site.
For more information on the OracleAS Cold Failover Cluster solution, see "Oracle Application Server Cold Failover Clusters" on page 3-7.
Installing Oracle Application Server 10g Software
asmid2.oracleas IN A 123.1.2.334
infra.oracleas IN A 123.1.2.111
remoteinfra.oracleas IN A 213.2.2.210
And, for the standby site, its DNS server should have the following entries:
asmid1.oracleas IN A 213.2.2.443
asmid2.oracleas IN A 213.2.2.444
infra.oracleas IN A 213.2.2.210
remoteinfra.oracleas IN A 123.1.2.111