Questions of NFTL and NAND Flash

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Dear All,

   I have traced the code of NFTL (NAND Flash Translation Layer), and I  
found that NFTL will write the spare area of NAND flash (OOB data) several 
times. However, I found that there are limited number of partial programming 
in spare area of NAND Flash (described in many specifications of NAND 
Flash). Does the data will write into spare area successfully without a 
erasing? 

Please help me, Thanks!
                                                              Joe