DDM conversation length considerations
Consider these items regarding the length of conversations when using DDM.
- Within a source job, if it is likely that a DDM conversation will be used by more than one program or DDM file, *KEEP is the value that should be specified for the DDMCNV job attribute. This saves the time and resources needed to start a target job (TDDM) each time a DDM file is accessed for the same location and mode combination within the source job.
- There is significant system and communications line overhead when a target DDM manager is started. The processing includes the APPC program start request, system type identification, and file open processing. However, if it is not necessary to keep the conversation active, *DROP should be specified for DDMCNV. When the local DDM file is closed, the session being used is released for use by other jobs using DDM or other APPC functions, such as SNADS and display station pass-through, to the same remote system.
- When the client and server systems are IBM® i operating
systems or System/38 platforms,
the file input and output requests made by an application program use a form
of DDM support that minimizes the amount of time needed to code and decode
each request. This is accomplished by System/38 extensions
to the DDM architecture.
When the client and server systems are neither an IBM i operating system nor a System/38, then System/38 extensions to the DDM architecture are not used.