Oracle Errors

• ORA - 12514: TNS:listener does not currently know of service requested in connector descriptor.

Solution: is to check "tnsnames.ora" file from ORACLE's directory. My Oracle 10g 's directory is C:\oraclexe\app\oracle\product\10.2.0\server\NETWORK\ADMIN\tnsnames.ora

if you use SYS user in XE database the parameters in the tnsnames.ora must be like following,
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = hostname)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
)
)
You can understand the syntax of the tnsnames.ora from your local directory.
C:\oraclexe\app\oracle\product\10.2.0\server\NETWORK\ADMIN\SAMPLE\tnsnames.ora