The System i Navigator will display the information about your AS400's stored procedures but I more often use some version of this SQL statement, modifying the WHERE clause as needed.
select substr(A.SPECIFIC_SCHEMA,1,10) AS "LIB",
substr(A.SPECIFIC_NAME,1,15) AS "PROC",
B.ORDINAL_POSITION AS "POS",
B.PARAMETER_MODE AS "MODE",
substr(B.PARAMETER_NAME,1,15) AS "PARMNAME",
substr(B.DATA_TYPE,1,15) AS "TYPE",
B.CHARACTER_MAXIMUM_LENGTH AS "CHARLEN",
B.NUMERIC_PRECISION AS "PRECISION",
B.NUMERIC_SCALE AS "SCALE"
from qsys2/sysprocs A
join qsys2/sysparms B
on A.SPECIFIC_SCHEMA = B.SPECIFIC_SCHEMA
and A.SPECIFIC_NAME = B.SPECIFIC_NAME
WHERE A.SPECIFIC_SCHEMA = 'GHELTON'
LIB PROC POS MODE PARMNAME TYPE CHARLEN PRECISION SCALE
GHELTON SEARCHOTBANDOVL 1 IN P_PVID INTEGER - 10 0
GHELTON SEARCHOTBANDOVL 2 IN P_TAXID CHARACTER 50 -
GHELTON SEARCHOTBANDOVL 3 IN P_FMTZIP5 CHARACTER 5 -
GHELTON SEARCHOTBANDOVL 4 IN P_FMTZIP9 CHARACTER 9 -
GHELTON SEARCHOTBANDOVL 5 IN P_ORIGIN CHARACTER 20 -
GHELTON SEARCHOTBANDOVL 6 IN P_TPA CHARACTER 10 -
GHELTON SEARCHOTBANDOVL 7 IN P_BILENT CHARACTER 20 -
GHELTON SEARCHOTBANDOVL 8 IN P_TARGETAMOUNT DECIMAL - 20 2
GHELTON SEARCHOTBANDOVL 9 IN P_TARGETDATE CHARACTER 10 -
GHELTON SQLRPGJDBC 1 IN - CHARACTER 15 -
GHELTON SQLRPGJDBC 2 IN - CHARACTER 15 -
GHELTON UPDATEOUTSIDEVE 1 IN ID INTEGER - 10 0
GHELTON UPDATEOUTSIDEVE 2 IN PHONE CHARACTER VARYI 20 -
GHELTON UPDATEOUTSIDEVE 3 IN USERID CHARACTER VARYI 20 -
GHELTON UPDATEOUTSIDEVE 1 IN ID INTEGER - 10 0
GHELTON UPDATEOUTSIDEVE 2 IN FAX CHARACTER VARYI 20 -
GHELTON UPDATEOUTSIDEVE 3 IN PHONE CHARACTER VARYI 20 -
GHELTON UPDATEOUTSIDEVE 4 IN USERID CHARACTER VARYI 20 -
******** End of data ********
