deleted xml definition in CONTEXT_FILE after adautocfg.sh for R12

i write xml definition for custom top in CONTEX_FILE, but it is deleted after run adautocfg.sh.

xml syntax:
<XXXXX_TOP oa_var="s_xxxxx_top" oa_type="PROD_TOP" oa_enabled="FALSE">$APPL_TOP/xxxxx/12.0.0</XXXXX_TOP>

SOLUTİON:

write in topfile.txt and run  adautocfg.sh. ($APPL_TOP/admin/topfile.txt)
synatx:
xxxxx    $APPL_TOP