Copyright © TIBCO Software Inc. All rights reserved
Copyright © TIBCO Software Inc. All rights reserved


Chapter 1 Overview : Message Delivery Considerations

Message Delivery Considerations
This section describes the types of message delivery provided by TIBCO Adapter for Files (IBM i).
Data Transfer Modes
You can use TIBCO Adapter for Files (IBM i) to transfer the data in files using the following modes:
Block Mode: the file is read in blocks without regard to its record or field structure. The data are published as blocks and must be subscribed to in block transfer mode as well.
Record Mode: the records and field structure of the data are read and published.
In addition, each of the above data transfer modes has a guaranteed and reliable mode, as follows:
Explicit Confirmation Mode (ECM): guaranteed mode for RV transport
Durable Subscribers: guaranteed delivery for EMS transport
For additional information, see Block Transfer Mode.
 
Transport Options
You can use TIBCO Adapter for Files (IBM i) to publish or subscribe to data using the following message delivery types:
Standard Rendezvous reliable delivery (RV): reliable message delivery that works well for many programs.
Rendezvous certified message delivery (RVCM): provides stronger assurances of delivery, along with tighter control, greater flexibility, and fine-grained reporting.
TIBCO Enterprise Message Service (EMS): provides guaranteed and reliable delivery
For additional information, see TIBCO Rendezvous Concepts and TIBCO Enterprise Message Service User’s Guide.
 
Comparing ECM and RVCM for Guaranteed Delivery
As noted previously, ECM cannot be used with RVCM, and therefore must be used with standard Rendezvous reliable delivery. ECM provides FTP-like functionality with error handling and recovery. While RVCM supports certified messaging, it can be slow when handling large data sets. ECM provides a simplified confirmation mechanism that is suitable for handling large data sets, and the adapter can handle data sets of any size.
By default, the adapter uses RVCM to guarantee message delivery. With RVCM, all messages are held in the publisher's ledger file, along with each subscriber’s state, until they are confirmed by all subscribers. While RVCM guarantees message delivery, its major disadvantage is that it requires significantly more disk space and memory. RVCM works well in environments that do not require high volume data rates. Its main strength is that it sends messages asynchronously and handles confirmations in the ledger without the application having to deal with it.
In block transfer mode, the adapter must support high volumes of data (files of 200MB or more), and its performance in transferring files is critical. If RVCM were used to transfer such large data sets, it would require an impractical and unfeasible amount of system resources. Also the data that the adapter is publishing is already held on disk in the input file, so storing it again in the RVCM ledger adds significantly more overhead.
The following differences between ECM and RVCM are notable:
ECM for block transfer requires that each subscriber confirm each block message. The publisher sends out a set of blocks containing file data, and it does not send the next set until it has received confirmations from each subscriber. If the publisher does not receive a block confirmation within a specified time limit, the publisher resends the block message (or messages). This mechanism ensures that the process memory does not to grow based on how fast the subscribers can process the data. Also, because the block data is already persisted in the input file and the publisher (FilePublisher) maintains its state, guaranteed delivery and recovery are achieved.
_TIBCO_AE_ADAPTER_FAFT_SUBTOPUB.<endpoint subject name>
_TIBCO_AE_ADAPTER_FAFT_PUBTOSUB.<endpoint subject name>
For additional information, see File Transfer Using ECM.

Copyright © TIBCO Software Inc. All rights reserved
Copyright © TIBCO Software Inc. All rights reserved