This topic includes tips for the best performance
of join logical files.
You can do the following things to improve the performance of join logical
files:
If the physical files you join have a different number of records, specify
the physical file with fewest records first (first parameter following the
JOIN keyword).
Consider using the DYNSLT keyword.
Consider describing your join logical file so it can automatically share
an existing access path.
Note: Join logical files always have access paths
using the second field of the pair of fields specified in the JFLD keyword.
This field acts like a key field in simple logical files. If an access path
does not already exist, the access path is implicitly created with immediate
maintenance.