What is difference of temporary lob in plsql

Question

hi all,
what is difference of temporary lob for plsql, i mean for ex what is difference for theese codes:
Declare
MyClob Clob;
X pls_integer;
begin
MyClob := 'something clob operation';
x := DBMS_Lob.InStr(MyClob, 'lob');
end;
Declare
MyClob Clob;
X pls_integer;
begin
DBMS_Lob.CreateTemporary(MyClob, True);
MyClob := 'something clob operation';
x := DBMS_Lob.InStr(MyClob, 'lob');
DBMS_Lob.FreeTemporary(MyClob);
end;
i know that temporary clob is stored in temporary tablespace but in the first code block above, what is difference ?
thanks

Answer 1

what is difference ? In this case there's no difference, because the temporary lob is created »silently«: From the Temporary LOB Performance Guidelines:
If you use the newly provided enhanced SQL semantics functionality in your applications, then there are many more temporary LOBs created silently in SQL and PL/SQL than before.
In particular, these temporary LOBs are silently created when you use the following:
SQL functions on LOBs
PL/SQL built-in character functions on LOBs
Variable assignments from VARCHAR2/RAW to CLOBs/BLOBs, respectively.
Perform a LONG-to-LOB migration
Things get different, when no »silent« creation takes place as e.g. in
SQL> declare
  2     myclob   clob;
  3     myclob2 clob;
  4  begin
  5     myclob := 'something clob operation';
  6     dbms_lob.append(myclob2, myclob);
  7  end;
  8  /
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 639
ORA-06512: at line 6then you can either use createtemporary procedure
SQL> declare
  2     myclob   clob;
  3     myclob2 clob;
  4  begin
  5     dbms_lob.createtemporary(myclob2,true);
  6     myclob := 'something clob operation';
  7     dbms_lob.append(myclob2, myclob);
  8  end;
  9  /
PL/SQL procedure successfully completed.Or force some other initialization:
SQL> declare
  2     myclob   clob;
  3     myclob2 clob;
  4  begin
  5     myclob := 'something clob operation';
  6     myclob2 := trim(to_clob(' '));
  7     dbms_lob.append(myclob2, myclob);
  8  end;
  9  /
PL/SQL procedure successfully completed.