For HiRDB system switchovers, you can use either the standby system switchover facility or the standby-less system switchover facility.

Standby system switchover facility

A standby HiRDB is provided in addition to the HiRDB that is performing business processing, and the business processing switches automatically to the standby HiRDB if an error occurs in the HiRDB performing the business processing. If you want to shorten the time it takes for a normal system switchover, you can also use user server hot standby or the rapid system switchover facility. For details about the standby system switchover facility, see 26.1.2 Standby system switchover facility.

Standby-less system switchover facility

If an error occurs in the HiRDB that is performing the business processing, the system switches to another unit that is running. There is no need to prepare a standby HiRDB. The standby-less system switchover facility can be used only in a HiRDB parallel server configuration. The standby-less system switchover facility can be further classified into the standby-less system switchover (1:1) facility and the standby-less system switchover (effects distributed) facility. For details, see 26.1.3 Standby-less system switchover facilities.

By using the user server hot standby method, the rapid system switchover facility, or the standby-less system switchover facility instead of normal system switchover, you can reduce system downtime. The following figure shows a comparison of system switchover times using these methods.

Figure 26-1 Comparison of system switchover times

Explanation

Because the processes indicated with shading are executed in advance during standby, these processes are not executed during a system switchover. The time required to perform a system switchover is reduced by the amount of time required to perform these processes.

The two operation modes for the system switchover facility are called the monitor mode and the server mode. In the monitor mode, only system errors are monitored. In the server mode, both system errors and server errors are monitored. The server mode can shorten the time required to perform a system switchover compared with the monitor mode. The following table lists the errors that can be monitored in the monitor mode and server mode.

Table 26-2 Errors that can be monitored in the monitor mode and server mode

System switchover facility operation mode	Monitored error
	System error#1	Server error#2
Monitor mode	Yes	No
Server mode	Yes	Yes

Legend:

Yes: Monitored.

No: Not monitored.

#1

The errors listed below are defined as system errors, but the conditions under which a system error occurs depend on the cluster software specifications. Check the documentation for the applicable cluster software.

• Hardware error
• OS error
• Power outage
• Cluster software error
• System slowdown

#2

The following errors are defined as server errors:

• HiRDB (unit for a HiRDB parallel server configuration) error
• HiRDB (unit for a HiRDB parallel server configuration) slowdown
• Database path error

(a) Cluster software products supported in the monitor mode and the server mode

In this manual, a product that performs system switchovers is called cluster software. The following table lists the cluster software products supported by HiRDB, and indicates whether they can be used in the monitor mode and the server mode.

Table 26-3 Cluster software products and their usability in the monitor mode and the server mode

Cluster software product	Monitor mode	Server mode
HA Monitor	Y	Y
MC/ServiceGuard	Y	Y
VERITAS Cluster Server	Y	Y
Sun Cluster	Y	N
HACMP	Y	N
PowerHA	Y	N
ClusterPerfect	Y	N
LifeKeeper	Y	N

Legend:

Y: The product is supported in this mode.

N: The product is not supported in this mode.

For details about cluster software products supported by HiRDB, see 26.1.5 Cluster software products supported by HiRDB.

(b) Products required for operation in the server mode

The following table lists the products required to operate the system switchover facility in the server mode.

Table 26-4 Products required for operation in the server mode

System switchover facility type	HiRDB Advanced High Availability	Hitachi HA Toolkit Extension
Normal system switchover	--	Required#
User server hot standby	--	Required#
Rapid system switchover facility	--	Required#
Standby-less system switchover (1:1) facility	Required	Required#
Standby-less system switchover (effects distributed) facility	Required	Required#

Legend:

Required: This product is required in order to operate the system switchover facility in the server mode.

--: This product is not required.

#

When the cluster software product being used is HA Monitor, Hitachi HA Toolkit Extension is not required.