dbms_lob.instr(
lob_loc in blob, 
pattern in raw, 
offset in integer := 1;
nth in integer := 1)
return integer;
 dbms_lob.instr(
lob_loc in clob character set any_cs,
pattern in varchar2 character set lob_loc%charset,
offset in integer:=1,
nth in integer := 1)
return integer;

dbms_lob.substr(
 lob_loc in blob, 
 amount in integer := 32767,
 offset in integer := 1)
return raw;
 dbms_lob.substr(
 lob_loc in clob character set any_cs, 
 amount in integer := 32767,
 offset in integer := 1)
return varchar2 character set lob_loc%charset;

 declare 
 source_lob clob;
 pattern varchar2(6) := 'Oracle';
 start_location integer := 1;
 nth_occurrence integer := 1;
 position integer;
 buffer varchar2(100);
begin
 select clob_locator into source_lob from mylobs where lob_index = 4;
 position := dbms_lob.instr(source_lob, pattern, start_location, nth_occurrence);
 dbms_output.put_line('The first occurrence starts at position:' || position);
 nth_occurrence := 2;
 select clob_locator into source_lob from mylobs where lob_index = 4;
 position := dbms_lob.instr(source_lob, pattern, start_location, nth_occurrence);
 dbms_output.put_line('The first occurrence starts at position:' || position);
 select clob_locator into source_lob from mylobs where lob_index = 5;
 buffer := dbms_lob.substr(source_lob, 9, start_location);
 dbms_output.put_line('The substring extracted is: ' || buffer);
end;
/
The first occurrence starts at position:8
The first occurrence starts at position:24
The substring extracted is: Oracle 9i