A list of values, such as "(a:b:c+2)". Each part of the composite key
may be any expression. Data types must match the corresponding key field,
but lengths, data format and CCSID do not have to match. 
A composite key is formed from the subfields
of the specified data structure in turn. Data types must match with the corresponding
key field, but lengths, data format, and CCSID do not have to match. Rules for moving
data from expression values to the key build area are the same as for operations
code EVAL in that shorter search arguments are padded on the right with blanks
and longer search arguments are truncated for type character. If num is
specified, that is the number of subfields to use in the composite key. 
Operation extenders H, M, and R are allowed for CHAIN, DELETE, READE, READPE, SETGT, and SETLL when a list of search arguments or %KDS is specified. These extenders apply to the moving of the individual search argument to the search argument build area.