You must consider which of the Real Time SAN Replication processing methods you will use: the all synchronous, all asynchronous, or hybrid method. The table below describes the characteristics of these processing methods.

Table 1-5 Characteristics of the all synchronous, all asynchronous, and hybrid methods

Main classification	Sub-classification	Real Time SAN Replication processing method
		All synchronous method	All asynchronous method	Hybrid method
Location of HiRDB files	Synchronous pair volume	Applicable	Not applicable	Applicable
	Asynchronous pair volume	Not applicable	Applicable	Applicable
	SMPL pair volume	Not applicable	Not applicable	Not applicable
Data loss#1		Does not occur	Can occur	Does not occur
Transaction processing performance	Performance deterioration caused by having to wait for update copying	Occurs	Does not occur	Occurs
	Performance comparison#2	44	100	88
Cost	Initial installation	Somewhat high	High	High
	Operation	High	High	High
Combination with other facilities	Facilities that cannot be concurrently executed	None	None	None
	Effects when UAP or SQL is executed in the no-log mode or pre-update log acquisition mode	None	None	Transaction performance deteriorates.#3
Operation	Operation of HiRDB at the disaster recovery site	Runs only when a disaster occurs	Runs only when a disaster occurs	Runs only when a disaster occurs
	Operation procedures	Simple	Simple	Somewhat complex

#1

If updated data is not correctly imported to the remote site due to an error or an operational mistake by a HiRDB administrator, data loss might occur, or it might not be possible to restart HiRDB at the remote site.

#2

Approximate relative value, where 100 indicates the transaction performance when Real Time SAN Replication is not used. This assumes an environment with 1-Gbps communication speed and a site-to-site transfer distance of 1,500 km. Note that the relative value depends on the attenuation rate between the main site and the remote site.

#3

For details, see 4.2 Notes on operation when using the hybrid method.