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What is a STEM?

As access to each individual STEM item looks like subscripting, there might be an assumption that it is an array, but this would be wrong.

A STEM variable is open ended, and each element can vary in size, so it should be viewed as a chain.

When using a STEM with EXECIO DISKR in z/OS the first element, i.e. stemname.0, will contain a count of the number of records read.

Similarly with EXECIO DISKW in z/OS the first element should contain a count of the number of records to be written.

On z/VM a null entry needs to be added as the last STEM item to mark the end of the data items.