Thats wierd ,
as per Oracle you can create spfile either before or after instance startup.
Pls check Note:166601.1 at metalink.
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1.Creation of the Spfile from a Pfile First of all you have to create a server parameter file (spfile). The spfile must be created from a traditional text initialization parameter file (pfile). You must have the SYSDBA or the SYSOPER system privilege to create a spfile. The command can be executed either before or after instance startup.