Advantages of using MFS
By using MFS, you can simplify the developing and maintaining of terminal-oriented applications, and improve online performance by using control blocks for online processing.
Simplify development and maintenance
To simplify IMS application development and maintenance, MFS performs many common application program functions and gives application programs a high degree of independence from specific devices or remote programs.
With the device independence offered by MFS, one application program can process data to and from multiple device types while still using their different capabilities. Thus, MFS can minimize the number of required changes in application programs when new terminal types are added.
MFS makes it possible for an application program to communicate with different types of terminals without having to change the way it reads and builds messages. When the application receives a message from a terminal, how the message appears in the program's I/O area is independent of what kind of terminal sent it; it depends on the MFS options specified for the program. If the next message the application receives is from a different type of terminal, you do not need to do anything to the application. MFS shields the application from the physical device that is sending the message in the same way that a DB program communication block (PCB) shields a program from what the data in the database actually looks like and how it is stored.
Other common functions performed by MFS include left or right justification of data, padding, exits for validity checking, time and date stamping, page and message numbering, and data sequencing and segmenting. When MFS assumes these functions, the application program handles only the actual processing of the message data.
The following figure shows how MFS can make an application program device-independent by formatting input data from the device or remote program for presentation to IMS, and formatting the application program data for presentation to the output device or remote program.
Improve online performance of a terminal
MFS also improves online performance of a terminal-oriented IMS by using control blocks designed for online processing. The MFS control blocks are compiled offline, when the IMS Transaction Manager system is not being executed, from source language definitions. MFS can check their validity and make many decisions offline to reduce online processing. In addition, during online processing, MFS uses look-aside buffering of the MFS control blocks to reduce CPU and channel costs of input/output activity.
Because MFS control blocks are reentrant and can be used for multiple applications, online storage requirements are reduced. Optional real storage indexing and anticipatory fetching of the control blocks can also reduce response time. Further performance improvements can be gained when IMS is generated for z/OS®, since multiple I/O operations can execute concurrently to load the format blocks from the MFS format library.
In addition, MFS uses z/OS paging services; this helps to reduce page faults by the IMS control region task.
MFS can reduce use of communication lines by compressing data and transmitting only required data. This reduces line load and improves both response time and device performance.