SDF-I uses up to two work files, which it creates and deletes as required These files are created under the name SYSSDF.SDF-I.tsn. (where version is the SDF-I version, e.g. 210 for SDF-I V21.0), tsn is the TSN of the calling task and n=1 or 2 is the number of the work file.
In general, users must make sure that there are no own files existing with these names. The two work files are used alternately when multiple syntax files are to be merged into the input syntax file (INPUT-FILE operand in the OPEN statement). The illustration below shows how they are used in the merge procedure.
How two work files are used in a merge run
These work files have the size of the output file. The execution of SDF-I therefore requires a sufficient reserve of disk storage space; otherwise, MERGE statement processing will be aborted.How two work files are used in a merge run