Overview of MFS components

You can use the MFS utilities for multiple service and generation purposes:

• MFS Device Characteristics Table utility (DFSUTB00): Define new screen sizes in a descriptor member of the IMS.PROCLIB library without completing an IMS system definition.
• MFS Language utility (DFSUPAA0): Create and store the MFS control blocks.
• MFS Service utility (DFSUTSA0): Control and maintain MFS intermediate text blocks and control blocks after they are processed and stored by the MFS Language utility (DFSUPAA0).

In addition to the using the MFS utilities to update MFS libraries, you can also use the IMS online change function. You can modify control block libraries while the IMS control region is executing.

You can customize the functions of the following MFS pool managers:

• MFS pool manager: MFS tries to minimize I/O to the format library by keeping referenced blocks in storage. This storage is managed by the MFS pool manager. You can use the INDEX function of the MFS Service utility to customize this function by constructing a list of the directory addresses for specified format blocks. This list eliminates the need for IMS to read the data set directory before it fetches a block.
• MFSTEST pool manager: If you use the MFSTEST facility, MFS control blocks are managed by the MFSTEST pool manager. The communication line buffer pool space allowed for MFS testing is specified during system definition, but the space can be changed when the IMS control region is initialized. This space value is the maximum amount used for MFSTEST blocks at any one time. The space value is not a reserved portion of the pool.