Oracle offers a high availability feature called Oracle Transparent Network Failover Failback (TNFF). In an IBM pSeries environment, this works closely with HACMP/ES.
Tip: The Oracle9i RAC network selection mechanism must be well understood before planning and configuring HACMP/ES.
Interconnect network selection
The Oracle cluster interconnect networks can be configured using either a "private" or a "public" network type defined in HCMP/ES. The Oracle IPC traffic is sent over one of the networks. Oracle RAC chooses the network interface according to the following rules:
1. HACMP "service" networks are required.
Oracle chooses only HACMP/ES networks configured as "service".
2. Oracle uses the HACMP cllsif utility to determine the network interface.
Oracle uses the HACMP utility cllsif to determine which network interface to use based on the rules described below. Oracle chooses the network to use according to the cllsif alphanumeric sort list.
3. Private networks are preferred over public networks.
If there are multiple private networks under HACMP, RAC chooses the interconnect communication by performance quality in the following order: SPswitch > FDDI > Ethernet
Note: Although networks can be labeled inside HACMP as public or private, this attribute has no functional meaning. It's only a way for Oracle to make network selections.
4. Maximum is three networks.
Oracle will choose up to three networks. Oracle recommends two private and one (or more) public networks for the cluster interconnect.
The Network failover and failback sequence
A typical configuration, using common network hardware, has two private interconnects and one public interconnect scenarios.
If the first HACMP/ES private service network goes down, Oracle TNFF fails over to the second private service network. If the second private service network also fails, TNFF continues to fail over to the public network.
If any of the two failed private interconnects is restored, the TNFF fails back to that private service interconnect. If both failed private interconnects are fixed, then TNFF restores the RAC communication to the first listed private service network, according to the cllsif command output alphanumeric sort order.
Tip: The Oracle9i RAC network selection mechanism must be well understood before planning and configuring HACMP/ES.
Interconnect network selection
The Oracle cluster interconnect networks can be configured using either a "private" or a "public" network type defined in HCMP/ES. The Oracle IPC traffic is sent over one of the networks. Oracle RAC chooses the network interface according to the following rules:
1. HACMP "service" networks are required.
Oracle chooses only HACMP/ES networks configured as "service".
2. Oracle uses the HACMP cllsif utility to determine the network interface.
Oracle uses the HACMP utility cllsif to determine which network interface to use based on the rules described below. Oracle chooses the network to use according to the cllsif alphanumeric sort list.
3. Private networks are preferred over public networks.
If there are multiple private networks under HACMP, RAC chooses the interconnect communication by performance quality in the following order: SPswitch > FDDI > Ethernet
Note: Although networks can be labeled inside HACMP as public or private, this attribute has no functional meaning. It's only a way for Oracle to make network selections.
4. Maximum is three networks.
Oracle will choose up to three networks. Oracle recommends two private and one (or more) public networks for the cluster interconnect.
The Network failover and failback sequence
A typical configuration, using common network hardware, has two private interconnects and one public interconnect scenarios.
If the first HACMP/ES private service network goes down, Oracle TNFF fails over to the second private service network. If the second private service network also fails, TNFF continues to fail over to the public network.
If any of the two failed private interconnects is restored, the TNFF fails back to that private service interconnect. If both failed private interconnects are fixed, then TNFF restores the RAC communication to the first listed private service network, according to the cllsif command output alphanumeric sort order.
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