Try below one (sample) :
Method 1:
<connectionStrings>
<add name="VoccDbContext" connectionString="metadata=res://*/Entities.Vocc.VoccModel.csdl|res://*/Entities.Vocc.VoccModel.ssdl|
 res://*/Entities.Vocc.VoccModel.msl;provider=Oracle.DataAccess.Client;provider connection string="DATA SOURCE=sameDbName;PASSWORD=somePass;USER ID=someUser;"" providerName="System.Data.EntityClient" />
</connectionStrings>
Check this for more :
http://stackoverflow.com/questions/11544191/connection-string-for-oracle-using-entity-framework-and-ldap[
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Method 2:
<add name="MyEntities" connectionString="metadata=res://*/OracleModel.csdl|res://*/OracleModel.ssdl|res://*/OracleModel.msl;provider=Oracle.DataAccess.Client;provider connection string="DATA SOURCE= (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = MY-SERVERNAME-OR-IP)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = PRODUCTION) ) );PASSWORD=MySecret*1;PERSIST SECURITY INFO=True;USER ID=JAMES.BOND"" providerName="System.Data.EntityClient" />
Check this for more :
http://shanthuk.com/2013/01/13/entity-framework-oracle-connection-string/[
^]
I hope this will help to you.