If an error occurs in a J2EE server and a process is down, the data on the EADs server does not become inconsistent even if the EADs client is being executed. Therefore, take action according to the procedure described in 2.2.1 Overview of troubleshooting and then start the J2EE server. For details on how to start a J2EE server, see 4.1.24 Starting a system (when CUI is used) in the uCosminexus Application Server System Setup and Operation Guide.

This subsection describes the following two types of actions to be taken for errors in an EADs server.

(a) When an error occurs in some of the EADs servers in a cluster

When an error occurs in some of the EADs servers in a cluster, operations can continue if one or more EADs servers are available in an EADs cluster. However, if the business is continued without restoring the EADs server with an error, the number of EADs servers reduces, and hence the availability decreases.

The following table describes the procedure of restoring an EADs server with an error separately for the case in which the restore operation is implemented while the business continues and the case in which the restore operation is implemented after stopping the business.

Table 2-10 Restore procedure when an error occurs in some of the EADs servers in a cluster

Business status when the EADs server is restored	Restore procedure	Notes
Business continues	Eliminate the cause of the error in the EADs server, and then use the locked restoration functionality and the functionality for securing data consistency provided by EADs to restore the global session information.#1	The HTTP session operations executed during an error restoration operation are not applied to the EADs server.#2
Business is stopped	Stop the J2EE application or the J2EE server. Eliminate the cause of the error in the EADs server, and then use the locked restoration functionality and the functionality for securing data consistency provided by EADs to restore the global session information.#1 Start the J2EE application or the J2EE server.	None

#1

For details on the functionality provided by EADs, see the Elastic Application Data store Users Guide.

#2

For details on the operations that are not applied to an EADs server, see (3) When data cannot be updated on an EADs server.

(b) When an error occurs in all the EADs servers

When an error occurs in all the EADs servers, the business can continue due to the HTTP session degeneracy of the EADs session failover functionality. However, if the business is continued without restoring the EADs server, and if an error occurs on a J2EE server, the session is not inherited on another duplicated J2EE server.

The following table describes the procedure of restoring an EADs server with an error separately for the case in which the restore operation is implemented while the business continues and the case in which the restore operation is implemented after stopping the business.

Table 2-11 Restore procedure when an error occurs in all the EADs servers

Business status when the EADs server is restored	Restore procedure	Notes
Business continues	Eliminate the cause of the error in the EADs server, and then reset up the EADs server environment. For details on setting up the EADs server environment, see 7.6 Preparing an EADs server in the uCosminexus Application Server Expansion Guide.	The operations of a session generated before the error occurred are not applied to the EADs server.#1 The HTTP session operations executed during an error restoration operation are not applied to the EADs server.#2
Business is stopped	Stop the J2EE application or the J2EE server. Eliminate the cause of the error in the EADs server, and then reset up the EADs server environment. For details on setting up the EADs server environment, see 7.6 Preparing an EADs server in the uCosminexus Application Server Expansion Guide. Start the J2EE application or the J2EE server.	All the global session information stored in the EADs server is lost, so a session cannot be re-created on the J2EE server.

#1

Only the HTTP session on the J2EE server is used for operations because no session information exists on the EADs server. Unlike a degenerated HTTP session, the information is not applied to the session information cache on the EADs server during the creation or update processing of the global session information when the next request is received.

#2

For details on the operations that are not applied to an EADs server, see (3) When data cannot be updated on an EADs server.

The following table describes the actions to be taken when data cannot be updated on an EADs server.

Table 2-12 Actions to be taken when data cannot be updated on an EADs server

Error contents Data update contents		Status after the occurrence of an error	Action after an error occurs
Update of data on all the EADs servers failed	Creating the global session information	The global session information is not created on all the EADs servers (session information storage destination server and copy destination server). The EADs session failover functionality continues the business by degeneracy.#1	None
	Updating the global session information	The global session information is not updated on all the EADs servers (session information storage destination server and copy destination server). The EADs session failover functionality continues the business by degeneracy.#1	None
	Deleting the global session information	The global session information is not deleted and remains behind on all the EADs servers (session information storage destination server and copy destination server). Note that if a request with the same session ID is received, the global session information is inherited on the J2EE server.	Use a command to delete the global session information. For details on how to delete the information, see 7.8.1 Deleting the global session information on an EADs server (session information storage destination server) in the uCosminexus Application Server Expansion Guide.
Update of data on an EADs server (session information copy destination server) failed	Creating the global session information	The global session information is not created on the session information copy destination server. The EADs session failover functionality continues the business by degeneracy.#1	None
	Updating the global session information	The global session information is not updated on the session information copy destination server. The EADs session failover functionality continues the business by degeneracy.# 1	None
	Deleting the global session information	The global session information is not deleted and remains behind on the session information copy destination server. Note that if an error occurs on the session information storage destination server, and if the copy destination server on which the global session information is remaining switches to the storage destination server, the global session information might be inherited on the J2EE server when a request with the same session ID is received.	Use a command to delete the global session information.#2 For details on how to delete the information, see 7.8.2 Deleting the global session information remaining on an EADs server (session information copy destination server) in the uCosminexus Application Server Expansion Guide.

#1

For details on the HTTP session degeneracy, see 5.7.3 Degeneracy of an HTTP session in the uCosminexus Application Server Expansion Guide.

#2

The global session information is not deleted for an EADs server (session information storage destination server and copy destination server) in which an error has occurred and which has been removed from the EADs cluster.