"cannot perform a DML operation inside a query" error when using table func

Question

hello please help me
i created follow table function when i use it by "select * from table(customerRequest_list);"
command i receive this error "cannot perform a DML operation inside a query"
can you solve this problem?
CREATE OR REPLACE FUNCTION customerRequest_list(
p_sendingDate varchar2:=NULL,
p_requestNumber varchar2:=NULL,
p_branchCode varchar2:=NULL,
p_bankCode varchar2:=NULL,
p_numberOfchekbook varchar2:=NULL,
p_customerAccountNumber varchar2:=NULL,
p_customerName varchar2:=NULL,
p_checkbookCode varchar2:=NULL,
p_sendingBranchCode varchar2:=NULL,
p_branchRequestNumber varchar2:=NULL
RETURN customerRequest_nt
PIPELINED
IS
ob customerRequest_object:=customerRequest_object(
NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);
condition varchar2(2000 char):=' WHERE 1=1 ';
TYPE rectype IS RECORD(
requestNumber VARCHAR2(32 char),
branchRequestNumber VARCHAR2(32 char),
branchCode VARCHAR2(50 char),
bankCode VARCHAR2(50 char),
sendingDate VARCHAR2(32 char),
customerAccountNumber VARCHAR2(50 char),
customerName VARCHAR2(200 char),
checkbookCode VARCHAR2(50 char),
numberOfchekbook NUMBER(2),
sendingBranchCode VARCHAR2(50 char),
numberOfIssued NUMBER(2)
rec rectype;
dDate date;
sDate varchar2(25 char);
TYPE curtype IS REF CURSOR; --RETURN customerRequest%rowtype;
cur curtype;
my_branchRequestNumber VARCHAR2(32 char);
my_branchCode VARCHAR2(50 char);
my_bankCode VARCHAR2(50 char);
my_sendingDate date;
my_customerAccountNumber VARCHAR2(50 char);
my_checkbookCode VARCHAR2(50 char);
my_sendingBranchCode VARCHAR2(50 char);
BEGIN
IF NOT (regexp_like(p_sendingDate,'^[[:digit:]]{4}/[[:digit:]]{2}/[[:digit:]]{2}$')
OR regexp_like(p_sendingDate,'^[[:digit:]]{4}/[[:digit:]]{2}/[[:digit:]]{2}[[:space:]]{1}[[:digit:]]{2}:[[:digit:]]{2}:[[:digit:]]{2}$')) THEN
RAISE_APPLICATION_ERROR(-20000,cbdpkg.get_e_m(-1,5));
ELSIF (p_sendingDate IS NOT NULL) THEN
dDate:=TO_DATE(p_sendingDate,'YYYY/MM/DD hh24:mi:ss','nls_calendar=persian');
dDate:=trunc(dDate);
sDate:=TO_CHAR(dDate,'YYYY/MM/DD hh24:mi:ss');
condition:=condition|| ' AND ' || 'sendingDate='||'TO_DATE('''||sDate||''',''YYYY/MM/DD hh24:mi:ss'''||')';
END IF;
IF (p_requestNumber IS NOT NULL) AND (cbdpkg.isspace(p_requestNumber)=0) THEN
condition:=condition|| ' AND ' || ' requestNumber='||p_requestNumber;
END IF;
IF (p_bankCode IS NOT NULL) AND (cbdpkg.isspace(p_bankCode)=0) THEN
condition:=condition|| ' AND ' || ' bankCode='''||p_bankCode||'''';
END IF;
IF (p_branchCode IS NOT NULL) AND (cbdpkg.isspace(p_branchCode)=0) THEN
condition:=condition|| ' AND ' || ' branchCode='''||p_branchCode||'''';
END IF;
IF (p_numberOfchekbook IS NOT NULL) AND (cbdpkg.isspace(p_numberOfchekbook)=0) THEN
condition:=condition|| ' AND ' || ' numberOfchekbook='''||p_numberOfchekbook||'''';
END IF;
IF (p_customerAccountNumber IS NOT NULL) AND (cbdpkg.isspace(p_customerAccountNumber)=0) THEN
condition:=condition|| ' AND ' || ' customerAccountNumber='''||p_customerAccountNumber||'''';
END IF;
IF (p_customerName IS NOT NULL) AND (cbdpkg.isspace(p_customerName)=0) THEN
condition:=condition|| ' AND ' || ' customerName like '''||'%'||p_customerName||'%'||'''';
END IF;
IF (p_checkbookCode IS NOT NULL) AND (cbdpkg.isspace(p_checkbookCode)=0) THEN
condition:=condition|| ' AND ' || ' checkbookCode='''||p_checkbookCode||'''';
END IF;
IF (p_sendingBranchCode IS NOT NULL) AND (cbdpkg.isspace(p_sendingBranchCode)=0) THEN
condition:=condition|| ' AND ' || ' sendingBranchCode='''||p_sendingBranchCode||'''';
END IF;
IF (p_branchRequestNumber IS NOT NULL) AND (cbdpkg.isspace(p_branchRequestNumber)=0) THEN
condition:=condition|| ' AND ' || ' branchRequestNumber='''||p_branchRequestNumber||'''';
END IF;
dbms_output.put_line(condition);
OPEN cur FOR 'SELECT branchRequestNumber,
branchCode,
bankCode,
sendingDate,
customerAccountNumber ,
checkbookCode ,
sendingBranchCode
FROM customerRequest '|| condition ;
LOOP
FETCH cur INTO my_branchRequestNumber,
my_branchCode,
my_bankCode,
my_sendingDate,
my_customerAccountNumber ,
my_checkbookCode ,
my_sendingBranchCode;
EXIT WHEN (cur%NOTFOUND) OR (cur%NOTFOUND IS NULL);
BEGIN
SELECT requestNumber,
branchRequestNumber,
branchCode,
bankCode,
TO_CHAR(sendingDate,'yyyy/mm/dd','nls_calendar=persian'),
customerAccountNumber ,
customerName,
checkbookCode ,
numberOfchekbook ,
sendingBranchCode ,
numberOfIssued INTO rec FROM customerRequest FOR UPDATE NOWAIT;
--problem point is this
EXCEPTION
when no_data_found then
null;
END ;
ob.requestNumber:=rec.requestNumber ;
ob.branchRequestNumber:=rec.branchRequestNumber ;
ob.branchCode:=rec.branchCode ;
ob.bankCode:=rec.bankCode ;
ob.sendingDate :=rec.sendingDate;
ob.customerAccountNumber:=rec.customerAccountNumber ;
ob.customerName :=rec.customerName;
ob.checkbookCode :=rec.checkbookCode;
ob.numberOfchekbook:=rec.numberOfchekbook ;
ob.sendingBranchCode:=rec.sendingBranchCode ;
ob.numberOfIssued:=rec.numberOfIssued ;
PIPE ROW(ob);
IF (cur%ROWCOUNT>500) THEN
CLOSE cur;
RAISE_APPLICATION_ERROR(-20000,cbdpkg.get_e_m(-1,4));
EXIT;
END IF;
END LOOP;
CLOSE cur;
RETURN;
END;

Answer 1

Now what exactly would be the point of putting a SELECT FOR UPDATE in an autonomous transaction?
I think OP should start by considering why he has a function with an undesirable side effect in the first place.