You are exceeding the SQL limit of 4000 bytes which applies to LISTAGG as well.
SQL> SELECT listagg(text, ',') WITHIN GROUP ( 2 ORDER BY NULL) 3 FROM 4 (SELECT to_char(to_date(level,'j'), 'jsp') text FROM dual CONNECT BY LEVEL < 250 5 ) 6 / SELECT listagg(text, ',') WITHIN GROUP ( * ERROR at line 1: ORA-01489: result of string concatenation is too long
As a workaround, you could use XMLAGG.
For example,
SQL> SET LONG 2000000
SQL> SET pagesize 50000
SQL> SELECT rtrim(xmlagg(XMLELEMENT(e,text,',').EXTRACT('//text()')
2 ).GetClobVal(),',') very_long_text
3 FROM
4 (SELECT to_char(to_date(level,'j'), 'jsp') text FROM dual CONNECT BY LEVEL < 250
5 )
6 /
VERY_LONG_TEXT
--------------------------------------------------------------------------------
one,two,three,four,five,six,seven,eight,nine,ten,eleven,twelve,thirteen,fourteen
,fifteen,sixteen,seventeen,eighteen,nineteen,twenty,twenty-one,twenty-two,twenty
-three,twenty-four,twenty-five,twenty-six,twenty-seven,twenty-eight,twenty-nine,
thirty,thirty-one,thirty-two,thirty-three,thirty-four,thirty-five,thirty-six,thi
rty-seven,thirty-eight,thirty-nine,forty,forty-one,forty-two,forty-three,forty-f
our,forty-five,forty-six,forty-seven,forty-eight,forty-nine,fifty,fifty-one,fift
y-two,fifty-three,fifty-four,fifty-five,fifty-six,fifty-seven,fifty-eight,fifty-
nine,sixty,sixty-one,sixty-two,sixty-three,sixty-four,sixty-five,sixty-six,sixty
-seven,sixty-eight,sixty-nine,seventy,seventy-one,seventy-two,seventy-three,seve
nty-four,seventy-five,seventy-six,seventy-seven,seventy-eight,seventy-nine,eight
y,eighty-one,eighty-two,eighty-three,eighty-four,eighty-five,eighty-six,eighty-s
even,eighty-eight,eighty-nine,ninety,ninety-one,ninety-two,ninety-three,ninety-f
our,ninety-five,ninety-six,ninety-seven,ninety-eight,ninety-nine,one hundred,one
hundred one,one hundred two,one hundred three,one hundred four,one hundred five
,one hundred six,one hundred seven,one hundred eight,one hundred nine,one hundre
d ten,one hundred eleven,one hundred twelve,one hundred thirteen,one hundred fou
rteen,one hundred fifteen,one hundred sixteen,one hundred seventeen,one hundred
eighteen,one hundred nineteen,one hundred twenty,one hundred twenty-one,one hund
red twenty-two,one hundred twenty-three,one hundred twenty-four,one hundred twen
ty-five,one hundred twenty-six,one hundred twenty-seven,one hundred twenty-eight
,one hundred twenty-nine,one hundred thirty,one hundred thirty-one,one hundred t
hirty-two,one hundred thirty-three,one hundred thirty-four,one hundred thirty-fi
ve,one hundred thirty-six,one hundred thirty-seven,one hundred thirty-eight,one
hundred thirty-nine,one hundred forty,one hundred forty-one,one hundred forty-tw
o,one hundred forty-three,one hundred forty-four,one hundred forty-five,one hund
red forty-six,one hundred forty-seven,one hundred forty-eight,one hundred forty-
nine,one hundred fifty,one hundred fifty-one,one hundred fifty-two,one hundred f
ifty-three,one hundred fifty-four,one hundred fifty-five,one hundred fifty-six,o
ne hundred fifty-seven,one hundred fifty-eight,one hundred fifty-nine,one hundre
d sixty,one hundred sixty-one,one hundred sixty-two,one hundred sixty-three,one
hundred sixty-four,one hundred sixty-five,one hundred sixty-six,one hundred sixt
y-seven,one hundred sixty-eight,one hundred sixty-nine,one hundred seventy,one h
undred seventy-one,one hundred seventy-two,one hundred seventy-three,one hundred
seventy-four,one hundred seventy-five,one hundred seventy-six,one hundred seven
ty-seven,one hundred seventy-eight,one hundred seventy-nine,one hundred eighty,o
ne hundred eighty-one,one hundred eighty-two,one hundred eighty-three,one hundre
d eighty-four,one hundred eighty-five,one hundred eighty-six,one hundred eighty-
seven,one hundred eighty-eight,one hundred eighty-nine,one hundred ninety,one hu
ndred ninety-one,one hundred ninety-two,one hundred ninety-three,one hundred nin
ety-four,one hundred ninety-five,one hundred ninety-six,one hundred ninety-seven
,one hundred ninety-eight,one hundred ninety-nine,two hundred,two hundred one,tw
o hundred two,two hundred three,two hundred four,two hundred five,two hundred si
x,two hundred seven,two hundred eight,two hundred nine,two hundred ten,two hundr
ed eleven,two hundred twelve,two hundred thirteen,two hundred fourteen,two hundr
ed fifteen,two hundred sixteen,two hundred seventeen,two hundred eighteen,two hu
ndred nineteen,two hundred twenty,two hundred twenty-one,two hundred twenty-two,
two hundred twenty-three,two hundred twenty-four,two hundred twenty-five,two hun
dred twenty-six,two hundred twenty-seven,two hundred twenty-eight,two hundred tw
enty-nine,two hundred thirty,two hundred thirty-one,two hundred thirty-two,two h
undred thirty-three,two hundred thirty-four,two hundred thirty-five,two hundred
thirty-six,two hundred thirty-seven,two hundred thirty-eight,two hundred thirty-
nine,two hundred forty,two hundred forty-one,two hundred forty-two,two hundred f
orty-three,two hundred forty-four,two hundred forty-five,two hundred forty-six,t
wo hundred forty-seven,two hundred forty-eight,two hundred forty-nine
If you want to concatenate multiple columns which itself have 4000 bytes, then you can concatenate the XMLAGG output of each column to avoid the SQL limit of 4000 bytes.
For example,
WITH DATA AS
( SELECT 1 id, rpad('a1',4000,'*') col1, rpad('b1',4000,'*') col2 FROM dual
UNION
SELECT 2 id, rpad('a2',4000,'*') col1, rpad('b2',4000,'*') col2 FROM dual
)
SELECT ID,
rtrim(xmlagg(XMLELEMENT(e,col1,',').EXTRACT('//text()') ).GetClobVal(), ',')
||
rtrim(xmlagg(XMLELEMENT(e,col2,',').EXTRACT('//text()') ).GetClobVal(), ',')
AS very_long_text
FROM DATA
GROUP BY ID
ORDER BY ID;