Illegal spool file name : "test.log APPEND" (bad character ' ')

Hello,

I would like to use the append option of spool but seem to not be enable to.

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Code :

SET DEFINE OFF 

SPOOL test.log APPEND

SET SERVEROUTPUT ON ;

...

SPOOL OFF ;

SET DEFINE ON 

SET SERVEROUTPUT OFF

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Error message :

Illegal spool file name: "test.log APPEND" (bad character: ' ')

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Oracle Database Version : 10g Enterprise Edition release 10.2.0.4.0

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Thank you for your help