Nonstop Database, HiRDB Version 9 Description
This subsection provides system configuration examples when the system switchover facility is being used.
This configuration provides a one-to-one correspondence between running systems and standby systems. Use this configuration when you wish to guarantee response times, even when a system has been switched over. However, you cannot use the resources on the standby server machines (one set of server machine resources cannot be used for every two server machines). The following figure illustrates a one-to-one system switchover configuration.
Figure 8-4 One-to-one system switchover configuration
This configuration provides a two-to-one correspondence between running systems and standby systems. The secondary system is configured as a multi-HiRDB system. Use this configuration with operations for which you wish to guarantee response times, even when a system has been switched over (response times deteriorate, though, if the two running systems have both been switched over). However, you cannot use the resources on the standby server machines (one set of server machine resources cannot be used for every three server machines). The following figure illustrates a two-to-one system switchover configuration.
Figure 8-5 Two-to-one system switchover configuration
This configuration provides an alternating standby system on each server machine while, at the same time, the server machine is operating as a running system. Every server machine is configured as a multi-HiRDB system consisting of a HiRDB running system and a HiRDB standby system. Use this configuration when you wish to utilize server machine resources most efficiently. However, response times deteriorate when a system has been switched over. The following figure illustrates a mutual system switchover configuration.
Figure 8-6 Mutual system switchover configuration
In this configuration, a single running system has multiple standby systems. You can apply this configuration to guard against a failure in a standby system before the running system recovers from a failure (multi-point failures). Standby systems are assigned different levels of priority, and when a failure occurs in the running system, the system is switched to the standby system having the highest priority. The following figure shows the multi-standby configuration.
Figure 8-7 Multi-standby configuration
This subsection provides examples of typical system configurations when the standby-less system switchover (1:1) facility is used.
This configuration example employs reciprocal alternate BESs on two back-end servers using standby-less system switchover (1:1). The following figure illustrates a system configuration example of such a mutual alternating configuration.
Figure 8-8 System configuration example of a mutual alternating configuration
This configuration example employs an alternate BES on one back-end server only using standby-less system switchover (1:1). The following figure illustrates a system configuration example of a one-way alternating configuration (2-node configuration).
Figure 8-9 System configuration example of a one-way alternating configuration (2-node configuration)
The following figure illustrates a system configuration example of the standby-less system switchover (effects distributed) facility. When a failure occurs in a regular unit, processing directed to the back-end servers of the failed primary system is distributed to and executed on multiple active server machines at their back-end servers.
Figure 8-10 System configuration example of the standby-less system switchover (effects distributed) facility
The following figure shows a configuration example of a mixed standby-less (1:1) and standby type setup.
Figure 8-11 System configuration example of a mixed standby-less (1:1) and standby type setup
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