The following table describes a comparison of the superiority of the database session failover functionality (when an integrity mode is enabled or disabled) and EADs session failover functionality. This table describes a comparison of the superiority when an integrity mode of the database session failover functionality is disabled.

Table 5-8 Comparing superiority of the session failover functionality

No.	Item to be compared	The database session failover functionality (as per the setting of integrity mode)		The EADs session failover functionality	Causes
		Enabled	Disabled
1	Request processing performance	W	--	B	In the case of the EADs session failover functionality, global session information is stored in memory because the memory can be accessed faster than disk.
2	Availability of system	B	--	W	Because availability of the EADs session failover functionality depends on the number of EADs servers (multiplicity), if you compare the same number of servers, there is a lower possibility of loss of global session information in the database session failover functionality that manages global session information in a database than the EADs session failover functionality that manages global session information in memory on the EADs server.
3	Integrity of global session information	B	--	--	Integrity of global session information is ensured only when an integrity mode of the database session failover functionality is enabled.

Legend:

B: Better than the standard value in functional requirements.

W: Worse than the standard value in functional requirements.

--: Standard value

The following table describes the available session failover functionality.

Table 5-9 Available session failover functionality

No.	Functionality	Overview	Usage status in the database session failover functionality (as per the setting of an integrity mode)		Usage status in the EADs session failover functionality	Reference location
			Enabled	Disabled
1	The session failover inhibition functionality	This functionality prevents degradation of request processing performance by inhibiting the session failover functionality in th ecase of requests that do not use an HTTP session	Y	Y	Y	5.6.1
2	Defining refer-only requests of an HTTP session	This functionality prevents degradation of the request processing performance by accessing the database or the EADs server by not letting update the global session information in the case of refer-only requests of an HTTP session	N	Y	Y	5.6.2
3	Concurrent execution of the same session ID	This functionality reduces impact on the request processing performance by concurrently executing requests of the same session ID	N	Y	Y	5.7.1
4	Inheriting global session information when stating a Web application	This functionality automatically inherits global session information when stating a Web application	N	Y	Y	5.7.2
5	Reducing an HTTP session	This functionality continues request processing only with HTTP sessions on the J2EE server when a failure occurs in the database or on the EADs server that stores global session information	N	Y	Y	5.7.3
6	Estimating the size of HTTP session attribute information	This functionality estimates the size when storing the attributes registered in an HTTP session, in a database or on an EADs server	Y	Y	Y	5.8.2
7	Deleting global session information	This functionality deletes global session information in a database or on an EADs server by using an SQL file or a command.	N	Y	Y	6.10.3, 7.8.1

Legend:

Y: Can be used.

N: Cannot be used.

For details on operations, functionality that you can use, and the precautions to be taken when you disable an integrity mode of the database session failover functionality, see 6.3 Selecting a mode in which performance is highly important (disabling an integrity mode).

For details on settings of an integrity mode, see 6.6 J2EE server settings.

Because storage locations of session information are different in the database session failover functionality and EADs session failover functionality, the operations when a failure occurs are different. The following table describes the operations of each functionality in the case of a failure occurrence.

Table 5-10 Operations in the case of failure occurrence

No.	Failure occurrence location		Operation of the database session failover functionality (as per the setting of an integrity mode)		Operation of the EADs session failover functionality
			Enabled	Disabled
1	J2EE server		You can resume the operations from the state immediately before the failure, on the J2EE server on which failure has not occurred.
2	Session information storage destination (database or EADs server)	Continuing operations	You cannot continue operations.	You can reduce and continue operations.	You cannot continue operations#. You can reduce and continue the operations even if all EADs servers, on which the session information is stored (including the session information copy destination EADs server), are down.
		Resuming operations after recovery	You can resume operations from the state immediately before the failure if you interrupt the operations and perform recovery.	You can resume operations from the state immediately before the failure if you interrupt the operations and perform recovery.	If a failure occurs on all EADs servers on the system, the session information is lost and hence you cannot recover to the state before the failure even if you interrupt the operations and perform recovery.

#

Even if a failure occurs on an EADs server on which session information is stored, data is secured until the reducing number of EADs servers reaches the number of multiplicity defined in EADs minus one. For details on multiplicity, see the Elastic Application Data store User Guide.