My final syntax :

EXPORT:

1. for full export :
exp system/manager file=full.dmp full=y consistent=y log=full.log

2. incremental export:
exp system/managr file=inc.dmp full=y inctype=incremental consistent=y log=inc.log

Import :
1. for full import:
imp system/manager file=full.dmp full=y log=fullimp.log

2. for incremental import:
imp system/manager file=inc.dmp full=y inctype=system log=incimp.log
imp system/manager file=inc.dmp full=y inctype=restore
log=inctype2.log