hi,
I created this tablespace:
CREATE TABLESPACE TBS DATAFILE 'C:\....\XXX01.dbf' SIZE 500M REUSE DEFAULT STORAGE (INITIAL 10240 NEXT 10240 MINEXTENTS 1 MAXEXTENTS 256 PCTINCREASE 0) ONLINE;

When I try to insert a new record in table ST I get this error:

ORA-01631:maxextents(256) reached in table TOM.ST

I tried to increase maxextents: (user=system)
ALTER TABLE TOM.ST STORAGE(MAXEXTENTS 500);

but I get this error:
ERROR at line 1:
ORA-25150: ALTERING of extent parameters not permitted

How can I resolve this error?
Thanks
Raf