ECS/ie High Availability

ECS/ie High Availability enables the configuration of multiple ECS/ie Clients over a single iSeries Server environment. Only one Client is active at any one time, Secondary Client(s) can be configured to monitor the Active client and automatically take over if it fails to respond after a predefined Time Out period.

The following defines Client side problems as instances where the secondary PC should take over:

• If Outlook is not functioning/responding causing ECS/ie to hang.

• If ECS/ie (BASE, EDI and XML) does not function.

• If the PC is not functioning/responding (Power or Windows problem).

• If the connection between the Client on the PC and the AS/400 Server is corrupted/terminated.

There are three types of ECS/ie Client within High Availability:

• Primary Client is the ECS/ie Client that is the "preferred" client. The PC defined as the Primary Client will always take on the ECS/ie client processing whenever it is able to.

• Active Client is the PC that is currently responsible for processing the ECS/ie tasks. This will normally be the PC defined as the Primary Client but if this is immobilised then it could be a Secondary Client.

• Secondary Client is responsible for monitoring the Active Client. The Secondary Client will take over as Active Client if the current Active Client has Timed out. Secondary Clients do not need to be configured within ECS/ie High Availability, any PC that is running ECS/ie that is not defined as the Primary Client is assigned a Secondary Client status. Any number of Secondary Clients can be set up over a single environment.

Transfer of control from Primary to Secondary Client

ECS/ie, ECSEDI and ECSXML will periodically update a "Last Active" time stamp value on the ECS/ie parameter file. It is the responsibility of  the Secondary Client(s) to periodically check the difference between the current time and the last active time stamp to compare it with the the predefined Primary Client Timeout period. If the current Active Client has Timed out then the Secondary Client is transformed into the Active Client. This transformation process consists of the following steps:

• Change Active Client to Secondary Client TCP/IP Address.

• Update the Last Activity Time Stamp on the ECS/ie Parameter file.

• Send an email to System Administrator(s) informing them that the Primary Client is not responding and that the Secondary Client has taken over as Active Client.

• Update the Windows Event Log with an Application Warning message stating that Primary PC with IP address is not responding that that control has switched to a Secondary Client.

• Update PC Registry on the new Active Client with values from AS/400 system parameter file (IESP)

When a Secondary Client is running as an Active Client then it will periodically check if control has been taken back by the Primary client. If this does happen then processing of the current cycle is interrupted and the Secondary Client resumes to monitoring the Primary Client.

Transfer of control from Secondary to Primary Client

The Primary Client will always take back control of ECS/ie processing whenever it is available. Once the issues with the Primary Client have been resolved it will take back control by performing the following tasks:

• Change Active Client back to Primary Client TCP/IP Address.

• Update the Last Activity Time Stamp on the ECS/ie Parameter file.

• Send an email to System Administrator(s) informing them that the Primary Client has resumed control.

• Update the Windows Event Log with an Application Information message stating that Primary PC with IP address has resumed control.

• Update PC Registry on the Primary Client (now the Active Client) with values from AS/400 system parameter file (IESP)

• Jump to “Looping” phase to allow completion of any tasks that the Active Secondary Client may be performing.

ECS/EDI Control Numbering

The standard ECS/EDI Processor retrieves & updates system parameter values locally in the PC registry, ECS/ie then synchronises the values in the PC Registry with the AS/400 Server based System Parameter file (IESP) at the beginning and end of the ECS/ie processing cycle. If the Primary Client should fail immediately following the execution of the ECS/EDI Processor and before ECS/ie has managed to Synchronise the system parameter values that there is a risk that the interchange/message control numbers on the AS/400 will be out of date and duplicates could be generated, resulting in subsequent interchanges being lost or rejected by external Trading Partners.

The enablement of ECS/ie High Availability will result in the ECS/EDI Processor control numbers being retrieved and updated directly on the AS/400 Server based Parameter file (IESP). The update of these values directly with the server will result in a slight deterioration on performance compared with storing the control numbers locally in the registry but does reduce the risk of losing interchange/message control numbers.

Configuration

When ECS/ie High Availability is enabled for the first time the Primary and Active Client TCP/IP addresses default to the PC TCP/IP address in use at the time. It is recommended that the PC that is to be defined as the Primary Client is configured first, meaning that no other configuration is needed.

The following ECS/ie High Availability configuration panel can be displayed by selected "Settings" from the main ECS/ie panel, then "ECS/ie System Settings" from the drop down menu and then click the "High Availability" Check box. 

• The Primary Client is the TCP/IP address of the PC that has been configured to perform the ECS/ie Client tasks.  Any other PC's that have ECS/ie installed and running are classified as Secondary Clients.

• The Primary Client Timeout period is the number of minutes that the Secondary Client(s) will monitor the Primary Client for before taking over as Active Client.

• The Current TCP/IP Address is the TCP/IP address of the PC that is currently being used. When you configure ECS/ie High Availability for the first time this TCP/IP address is used to define the Primary Client and Active Client.

• The Active Client is the TCP/IP address of the PC that is currently responsible for performing the ECS/ie Client tasks.

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