SQL> ALTER SYSTEM SET SERVICE_NAMES='oracleblog.org, jimmy.oracleblog.org, jimmy.he.oracleblog.org, hejianmin.oracleblog.org, he.jian.min.oracleblog.org, jimmy_he_oracleblog.org, jimmy_he_he.jian_min.oracleblog.org, jian_min_he.jimmy.oracleblog.org, jimmy.he.he_jianmin.oracleblog.org, jimmyhe_hejianmin.oracleblog.org, jimmy.he.he.jianmin.oracleblog.org' scope=both;
ALTER SYSTEM SET SERVICE_NAMES='oracleblog.org, jimmy.oracleblog.org, jimmy.he.oracleblog.org, hejianmin.oracleblog.org, he.jian.min.oracleblog.org, jimmy_he_oracleblog.org, jimmy_he_he.jian_min.oracleblog.org, jian_min_he.jimmy.oracleblog.org, jimmy.he.he_jianmin.oracleblog.org, jimmyhe_hejianmin.oracleblog.org, jimmy.he.he.jianmin.oracleblog.org' scope=both
*
ERROR at line 1:
ORA-32021: parameter value longer than 255 characters
SQL>

SQL> ALTER SYSTEM SET SERVICE_NAMES='oracleblog.org', 'jimmy.oracleblog.org', 'jimmy.he.oracleblog.org', 'hejianmin.oracleblog.org', 'he.jian.min.oracleblog.org', 'jimmy_he_oracleblog.org', 'jimmy_he_he.jian_min.oracleblog.org', 'jian_min_he.jimmy.oracleblog.org', 'jimmy.he.he_jianmin.oracleblog.org', 'jimmyhe_hejianmin.oracleblog.org', 'jimmy.he.he.jianmin.oracleblog.org' scope=both;
System altered.
SQL>
SQL> show parameter service_names
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
service_names                        string      oracleblog.org, jimmy.oraclebl
og.org, jimmy.he.oracleblog.or
g, hejianmin.oracleblog.org, h
e.jian.min.oracleblog.org, jim
my_he_oracleblog.org, jimmy_he
_he.jian_min.oracleblog.org, j
ian_min_he.jimmy.oracleblog.or
g, jimmy.he.he_jianmin.oracleb
log.org, jimmyhe_hejianmin.ora
cleblog.org, jimmy.he.he.jianm
in.oracleblog.org
SQL>
SQL>
SQL>
SQL>

--转自

Error Id: ORA-32021

Title: parameter value longer than string characters

Description:

parameter value longer than string characters

Action:

Reduce the parameter value length and retry the command. For the DISPATCHERS parameter, use listener aliases to reduce value length.

Cause:

An attempt was made to alter a parameter value but the number of characters in the parameter value was longer than the allowed maximum. For a list parameter, one of the values in the list was longer than the allowed maximum.

-- 来自：