Pre-requisites for expdp and impdp:

• Check the database status details using below query.

SQL>COL DB_UNIQUE_NAME FOR A15

SQL>COL PLATFORM_NAME FOR A20 

SQL>SELECT DBID,NAME,DB_UNIQUE_NAME,DATABASE_ROLE,OPEN_MODE,PROTECTION_MODE,

PLATFORM_NAME,FLASHBACK_ON 

FROM gV$DATABASE;

• Based on your requirement you can check the query for entire database or schema size using below queries. 

SQL> select sum(bytes/1024/1024/1024) from dba_data_files;

(OR)

SQL>

select owner,sum(bytes)/1024/1024/1024 schema_size_gb

from dba_segments group by owner;

• Check the database version using below query.

SQL> select banner from v$version;

• Check character set for the current database using below query.

SQL>select * from v$NLS_PARAMETERS;

• Check invalid object count on database prior export using below query.

SQL>select count(*) from dba_objects where status='INVALID';

• Check the space requirement where you're going to take the export at OS level or disk group, wherever depends on your requirement.

• Useful commands if you are checking at OS level: 
• df -kh   in Linux/Sun Solaris
• bdf   in HP- UX

• Directory creation at database and OS level using below command.

SQL>create or replace directory <directory_name> as <directory_path>;

SQL>exit;

$mkdir <direcotory_name>

Note: All above steps are just to check the feasibility before export, i will update how to take export and import the database/schema in my next post.