DBPROCPARAMS 
Using the
system table
DBPROCPARAMS, you can determine the following database information:
- All input parameters of your own
database procedure MYPROC and the following parameter information: data type, length and specification of which number in the sequence the parameter has within the database procedure
SELECT parametername, datatype, len, dec, pos
FROM DOMAIN.DBPROCPARAMS
WHERE owner = user
AND dbprocname = 'MYPROC'
AND "IN/OUT-TYPE" = 'IN'
Total number of parameters in your own database procedure MYPROC
SELECT COUNT(*)
FROM DOMAIN.DBPROCPARAMS
WHERE owner = user
AND dbprocname = 'MYPROC'

Database procedures: see
DBPROCEDURES