here are some examples on exp/imp:[@more@]
1. after drop the user, use below to create first.

create user cog84cs identified by welcome1 DEFAULT TABLESPACE COGNOS_APP TEMPORARY TABLESPACE TEMP;
GRANT UNLIMITED TABLESPACE TO cog84cs;

2. and get the privs info:
select * from DBA_SYS_PRIVS where grantee in ('COG84CS','CG84ADTD');
select * from DBA_TAB_PRIVS where grantee in ('COG84CS','CG84ADTD');
select * from DBA_ROLE_PRIVS where grantee in ('COG84CS','CG84ADTD');

nohup imp "/ as sysdba" file=/db01/cognos8.dmp log=/db01/cognos8)imp.log fromuser=(cog84cs,cg84adtd) touser=(cog84cs,cg84adtd) feedback=10000 buffer=100000000 &


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full db exp:
nohup exp "/ as sysdba" file=cogdbdexp.dmp log=cogdbdexp.log feedback=10000 consistent=y statistics=none indexes=y full=y buffer=100000000 Compress=Y &

full db imp:
before imp, use this statement to generate drop statement to drop all default oracle generated schemas:

select 'drop user '|| username||' cascade;' from dba_users where username not in ('SYS','SYSTEM','OUTLN','DIP','TSMSYS','DBSNMP','WMSYS','EXFSYS','XDB','ANONYMOUS','ORACLE_OCM','DBMON','DBA');

nohup imp "/ as sysdba" file=/db01/oraback/cogdbd/exp/cogdbdexp.dmp log=/tmp/cogdbdimp.log feedback=10000 buffer=100000000 full=y &


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exp "/ as sysdba" file=%DMPFILE% log=%LOGFILE% tablespaces=(SYSTEM,SYSAUX,USERS,ARC_SYSTEM_DATA,ARC_SYSTEM_INDEX) direct=Y STATISTICS=NONE