invalid LOB locator specified: ORA-22275

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Just a simple reminder (I tend to forget things over the centuries) when using procedure DBMS_LOB.CONVERTTOCLOB with persistent lob locators:

1. don't forget to include the FOR UPDATE clause in the SELECT statement fetching the lob locators. 
2. don't forget to initialize the destination lob (in this case the clob column DOC)  with EMPTY_CLOB().

otherwise ORA-22275 may occur (see also another cause of this error).

...
 select doc, bdoc, charset
   into l_clob, l_blob, l_cset
   from file_imports
  where id = p_fileid
    for update;

...
 dbms_lob.converttoclob(
  l_clob,
  l_blob,
  dbms_lob.lobmaxsize,
  l_coff,
  l_boff, 
  l_cset,
  l_context,
  l_warn);
...
 
ORA-06502: PL/SQL: numeric or value error: invalid LOB locator specified: ORA-22275 

In the PL/SQL fragment above, column DOC was null, which is a different value from EMPTY_CLOB().
As this column is always null when the record is created, I modified the default value of the column as follows:

alter table file_imports modify doc default empty_clob();

This avoids the annoyance of having to update the row and set DOC to EMPTY_CLOB() before calling DBMS_LOB.CONVERTTOCLOB.


See message translations for ORA-22275 and search additional resources.

LPX-00209: PI names starting with XML are reserved

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I don't know why it took me more than the necessary to understand where was the problem when I hit the following error.

ORA-31011: XML parsing failed
ORA-19202: Error occurred in XML processing
LPX-00209: PI names starting with XML are reserved

At any rate, in my case the reason was not the same as reported in other sites (like having a duplicate XML declaration).
The trouble was caused by a simple blank character located before the initial XML file declaration.
The error occurred on Oracle 10.2 (XE), while on Oracle 11.2.0.3.0 EE the blanks seem to give no concerns whatsoever to the parser.
I ignore the results on the Oracle versions in between.

You can easily simulate the problem with the following query in SQL Developer:

select xmltype(' ' || dbms_xmlgen.getxml('select 1 from dual')) x from dual;

If you have a clob object containing an xmlfile with extra blanks at the beginning of the file and attempting to parse it you get this error, you may easily fix the problem by TRIMming it first.

See message translations for ORA-19202, LPX-00209 and search additional resources.