Foreign key constraint issues in export/import

If export has been done at the table level and If child table (Table with foriegn key) has been exported first and parent table later ( Table with primary key) then there will be issue at importing because import of tables takes place in the same order as export has taken .There will be  constraints error in importing child tables. In that case we have to import first all for  parent table and in after that import chid tables . i.e we have to perform import twice. Once the  parents tables  and second time child tables  So to avoid this workaround, one should be prudent in picking the tables order in export.   

Example:

In the given eample  table x have  foriegn key reference  with the table y.   Tables export takes in the order x and y.

 exp scott/tiger@mediamat FILE=/home/oracle/expdrec/exp.dmp LOG=/home/oracle/expdrec/exp.LOG  CONSISTENT=y tables=x,y

Export: Release 10.2.0.4.0 - Production on Mon May 9 09:47:52 2011

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

Export done in US7ASCII character set and AL16UTF16 NCHAR character set

server uses WE8ISO8859P1 character set (possible charset conversion)

About to export specified tables via Conventional Path ...

. . exporting table                              X          2 rows exported

. . exporting table                              Y          2 rows exported

Export terminated successfully without warnings.

[oracle@mediamath-server archs]$ imp impuser/impuser@mediamat FILE=/home/oracle/expdrec/exp.dmp LOG=/home/oracle/expdrec/exp.LOG ignore=y  tables=y,x fromuser=scott touser=impuser

Import: Release 10.2.0.4.0 - Production on Mon May 9 11:26:26 2011

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

Export file created by EXPORT:V10.02.01 via conventional path

Warning: the objects were exported by SCOTT, not by you

import done in US7ASCII character set and AL16UTF16 NCHAR character set

import server uses WE8ISO8859P1 character set (possible charset conversion)

. importing SCOTT's objects into IMPUSER

. . importing table                            "X"     127136 rows imported

. . importing table                            "Y"     127209 rows imported

IMP-00017: following statement failed with ORACLE error 2298:

 "ALTER TABLE "Y" ADD FOREIGN KEY ("AA_ID") REFERENCES "X" ("AA_ID") ENABLE"

IMP-00003: ORACLE error 2298 encountered

ORA-02298: cannot validate (IMPUSER.SYS_C0059272) - parent keys not found

Import terminated successfully with warnings.