In case you want to search a string or any other number in all tables inside a schema. Then there is a free tool available for it. I have tried many scripts and PL/SQL procedures to do this, but by far the best is the freeware tool DBSEARCH. It can be downloaded free from the below link. It can even search inside SQL server since it connects to the database using ODBC drivers.
https://sites.google.com/site/freejansoft/dbsearch
or
https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxmcmVlamFuc29mdHxneDozYmQwNzNlMTk3NWUzMDhk
