UTL_FILE.WRITE_ERROR when calling utl_file.put in a loop

问题

I have below code in my PL/SQL procedure, which I called in API_XXX.put(it calls utl_file.put) in a while loop. And the l_xmldoc is CLOB from a function of getReportXML, which returns the xml clob.

the code I write to write xml into a file is like:

l_offset := 1;
    WHILE (l_offset <= l_length)
    LOOP
    l_char := dbms_lob.substr(l_xmldoc,1,l_offset);

    IF (l_char = to_char(10))  ---I also tried if (l_char=chr(10)) but it did not work 
    THEN
        API_XXXX.new_line(API_XXX.output, 1);
    ELSE
        API_XXXX.put(fnd_API_XXX.output, l_char);
    END IF;

    l_offset := l_offset + 1;
    END LOOP;

Please note that the API_XXX is the existing package which I am not able to modify, and this api calls fflush in the end of put.

API_XXX.put's part is like below("WHICH" is the first param):

         elsif WHICH = API_XXX.OUTPUT then
           temp_file := OUT_FNAME;
           utl_file.put(F_OUT, BUFF);
           utl_file.fflush(F_OUT);

API_XXX.new_line is like(LINES is the number of lines to write):

         elsif WHICH = API_XXX.OUTPUT then
           temp_file := OUT_FNAME;
           utl_file.new_line(F_OUT, LINES);
           utl_file.fflush(F_OUT);

I notice a that the put/new_line procedure in my customer's side will sometimes raise UTL_FILE.WRITE_ERROR for unknown reason(maybe due to the l_length is too large(up to 167465)) in the while loop from my customer.

I read Oracle PL/SQL UTL_FILE.PUT buffering . And I found that this is the same cause, my l_xmldoc is really large and when I loop it, I found that it is without a new line terminator so the buffer is up to 32767 even though I fflush every time.

So, how should I convert the l_xmldoc into a varchar with new line terminator.

PS: I confirmed that my customer is using Oralce 11g

回答1:

Post the Oracle Version you are using! Or we can just guess around...
Your fflush will not work as you expect - From the documentation:

FFLUSH physically writes pending data to the file identified by the file handle. Normally, data being written to a file is buffered. The FFLUSH procedure forces the buffered data to be written to the file. The data must be terminated with a newline character.
tbone is abolutely right the line TO_CHAR(10) is wrong! Just try SELECT TO_CHAR(10) FROM DUAL; you will get 10 which you then compare to a single character. A single character will never be '10' since 10 has two characters!
Your problem is most likely a buffer-overflow with too large XML-Files, but keep in mind, also other problems on the target system can lead to write_errors, which should be handled.

Solutions

Quick&Dirty: Since you don't seem to care about performance anyways you can just close the file every X byte and reopen it with A for append. So just add to the loop:
```
IF MOD( l_offset, 32000 ) = 0
THEN
  UTL_FILE.FCLOSE( f_out );
  UTL_FILE.FOPEN( out_fpath, out_fname, f_out, 'a', 32767 );
END IF;
```
Use the right tool for the right job: UTL_FILE is not suited for handling complex data. The only usecase for UTL_FILE are small newline-separated lines of text. For everything else you should write RAW bytes! (Which will also allow you porper control over ENCODING, which is currently just mini-vanilly-lucky-guess)
Write a Java-Stored-Procedure with NIO-Filechannels - fast, safe, nice... But be careful, your program might run 10 times as fast!

回答2:

Just a guess, but instead of "to_char(10)" you might try chr(10) to determine/write a newline. Not sure if this will solve your problem, but sometimes very long lines (without newlines) can cause issues.

For example:

declare
    l_clob clob;
    l_char char;
begin
    l_clob := 'Line 1' || chr(10) || 'Line 2' || chr(10);

    for i in 1 .. DBMS_LOB.GETLENGTH(l_clob)
    loop
        l_char := dbms_lob.substr(l_clob, 1, i);

        if (l_char = chr(10)) then
        --if (l_char = to_char(10)) then
            dbms_output.put_line('Found a newline at position ' || i);
        end if;
    end loop;

end;

Notice the difference between chr(10) and to_char(10). Easy enough to test if this solves your problem anyway.

来源：https://stackoverflow.com/questions/25279365/utl-file-write-error-when-calling-utl-file-put-in-a-loop

标签

sql

Oracle

plsql

utl-file