SQL> ed
Wrote file afiedt.buf

  1    DECLARE
  2     my_text_handle CLOB;
  3    my_buffer clob;
  4     my_add_amt NUMBER := 32000;
  5     my_offset INTEGER := 1;
  6   buf varchar2(32000);
  7     BEGIN
  8   select text into my_buffer  from SRIRAM_CLOB;
  9   buf := dbms_lob.substr(my_buffer);
 10        my_add_amt := length(buf);
 11     SELECT long_text
 12     INTO my_text_handle
 13     FROM text
 14     where  TEXT_SEQUENCE_NUMBER=246 and  text_id= 88 FOR UPDATE;
 15     DBMS_LOB.WRITE(my_text_handle, my_add_amt, my_offset, buf);
 16     COMMIT;
 17*    END;
SQL> /

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1    DECLARE
  2     my_text_handle CLOB;
  3    my_buffer clob;
  4     my_add_amt NUMBER := 32000;
  5     my_offset INTEGER := 1;
  6   buf varchar2(32000);
  7     BEGIN
  8   select text into my_buffer  from SRIRAM_CLOB;
  9   buf := dbms_lob.substr(my_buffer);
 10        my_add_amt := length(buf);
 11     SELECT long_text
 12     INTO my_text_handle
 13     FROM text 
 14     where  TEXT_SEQUENCE_NUMBER=14257 and  text_id= 88 FOR UPDATE;
 15     DBMS_LOB.WRITE(my_text_handle, my_add_amt, my_offset, buf);
 16     COMMIT;
 17*    END;
SQL> /
  DECLARE
*
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: invalid LOB locator specified:
ORA-22275
ORA-06512: at "SYS.DBMS_LOB", line 819
ORA-06512: at line 15

ORA-22275: invalid LOB locator specified
 *Cause:  There are several causes:  (1) the LOB locator was never
          initialized; (2) the locator is for a BFILE and the routine
          expects a BLOB/CLOB/NCLOB locator; (3) the locator is for a
          BLOB/CLOB/NCLOB and the routine expects a BFILE locator;
          (4) trying to update the LOB in a trigger body -- LOBs in
          trigger bodies are read only; (5) the locator is for a
          BFILE/BLOB and the routine expects a CLOB/NCLOB locator;
          (6) the locator is for a CLOB/NCLOB and the routine expects
          a BFILE/BLOB locator;
 *Action: For (1), initialize the LOB locator by selecting into the locator
          variable or by setting the LOB locator to empty.  For (2),(3),
          (5) and (6)pass the correct type of locator into the routine.
          For (4), remove the trigger body code that updates the LOB value.