Overview
Except for the TCP transport, all other transport types support store and forward. In the event of an enterprise outage or network failure, the store and forward feature saves all transactions on the node, and then delivers them when the connection to the enterprise host can be established again.
When the connection to the enterprise host is re-established, messages from the store and forward queue are delivered to the enterprise application until the queue is cleared.
By default, store and forward is turned on with the Process queue before leaving S/F option. See parameter details below.
Parameter values for the Store & Forward tab
The following shows an example SAP transport and its Store & Forward tab:
Store & Forward
When the Store & Forward check box
is selected, the transport will switch to store and forward
mode in case the connection to the enterprise host is
lost.
If unchecked, store and forward mode is not active and
transactions will be counted as failures in case the
connection to the enterprise host is lost.
TTL(sec)
You can use the Time to Live (TTL) parameters to control the use of the Store and Forward queue while the transport is suspended. The value in seconds determines how long to retain messages that are in the store and forward queue.
Max Storage (MB)
The Max Storage parameter is the maximum size of the store and forward queue for the current transport. The default is 20 MB. The only limit is the amount of disk space on the node.
On overflow
There are two options:
Discard new message — Do not accept any new messages once
the store and forward queue reaches its maximum size. New
messages are counted as failures.
Delete oldest message — Have the oldest messages discarded
in a first in/first out (FIFO) manner when the store and
forward queue becomes full.
Process queue before leaving S/F
When creating a transport, the Process queue
before leaving S/F check box can be used to modify
the behavior of store and forward.
By default, the Process queue before leaving
S/F check box is selected and data in the store
and forward queue behaves in a first in/first out (FIFO)
manner. This means that once the connection is
re-established to the end point application, data is
delivered in the order in which it entered the store and
forward queue.
When the Process queue before leaving S/F check box is not selected, as soon as the connection is re-established with the end point application, new data is not added to the store and forward queue but; instead, is sent directly to the end-point application, and the data residing in the store and forward queue is also being delivered to the end point application. The order of delivery is not important in this non-FIFO mode. It is possible to have the state of a transport shown as Up (on the Transports tab) while data is still in the store and forward queue.
Non-FIFO mode guarantees to empty the store and forward queue. However, in FIFO mode, clearing the queue depends on the rate data is added to the queue. For FIFO mode, when data is added to the queue at a rate faster than it is being delivered, the transport will always remain in store and forward.
To fine tune an application's ability to switch to store
and forward mode, use the Connection and
Execution timeouts parameters from the
Timeout tab.
The following Related Topics links
pertain to tabs available from different transport type
windows. For example, a transport window for a TCP
transport has Timeout and Custom Payloads tabs; while a
WebSphere MQ transport type has a Timeout, Store &
Forward, Mapping Log, and Custom Payloads tabs.