Input to a merge application can be up to 100 blocked or unblocked QSAM or VSAM data sets containing fixed- or variable-length records. The input data sets can be either QSAM or VSAM, but not both. The records in all input data sets must already be sorted in the same order as that required for output.

Output from a merge application can be blocked or unblocked QSAM or VSAM data sets, regardless of whether the input is QSAM or VSAM. Unless OUTFIL is used to convert variable input to fixed output, or fixed output to variable output, an output data set must be the same type (fixed or variable) as the input data set.

Files in a z/OS file system are supported as input and output for merge applications.