TNS

• static and dynamic listener registration - artincarstenbach.wordpress.com
• Exploring the LOCAL_LISTENER parameter - edstevensdba.wordpress.com
• diagnosing connection issues - edstevensdba.wordpress.com
• tracking down solutions to tns error messages - edstevensdba.wordpress.com

Some basic reminders

Original at edstevensdba.wordpress.com

• The listener itself doesn’t give a flying fig about what is in tnsnames.ora. That file (tnsnames.ora) is used ONLY by client processes. In the case of dynamic registration, the database IS the client process.
• The listener is quite capable of starting with no listener.ora file at all. In this case it will start with all default values, including the default name of LISTENER and default port of 1521. For most people, most of the time, this is sufficient.
• If the local_listener parameter is not set (null) the database will send the registration request to port 1521. Notice that 1521 is also the default port of of the listener.
• If you choose to set local_listener, you can either use a full connect string ((ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1421))) or simply reference an entry in tnsnames.ora, to resolve to the address (server name and port) of the listener.
• The SID_LIST section of listener.ora has nothing to do with dynamic registration. Quite the opposite. The SID_LIST section is how you implement static registration.

Connections fail 10% of the time. How to fix?

Turn on tracing
There are some settings that can help...

sqlnet.ora

Setting a value greater than 0 ensures that connections are not left open indefinitely, due to, for example, an abnormal client termination.

# sqlnet.ora Network Configuration File: /oracle/product/11.2.0.4/network/admin/sqlnet.ora
# Generated by Oracle configuration tools.

NAMES.DIRECTORY_PATH= (TNSNAMES, ONAMES, HOSTNAME)

ADR_BASE = /oracle/product

DIAG_ADR_ENABLED=OFF

sqlnet.expire_time=10
DEFAULT_SDU_SIZE=11280

tnsnames.ora

The clause for LISTENER_FEUK11UD is a reference for the local_listener parameter.

# tnsnames.ora Network Configuration File: /oracle/product/11.2.0.4/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

LISTENER_FEUK11UD =
  (ADDRESS = (PROTOCOL = TCP)(HOST = HFE2PrePrdOra)(PORT = 1521))


FEUK11UD =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = HFE2PrePrdOra)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = FEUK11UD)
    )
  )

Setting the local_listener in the database to the connection string instead of the connect identifier can help the debugging process...

alter system set local_listener="(ADDRESS = (PROTOCOL = TCP)(HOST = HFE2PrePrdOra)(PORT = 1521))" scope=both;

listener.ora

Setting STARTUP_WAIT_TIME_LISTENER Setting CONNECT_TIMEOUT_LISTENER

# listener.ora Network Configuration File: /oracle/product/11.2.0.4/network/admin/listener.ora
# Generated by Oracle configuration tools.

STARTUP_WAIT_TIME_LISTENER_FEUK11UD = 0
CONNECT_TIMEOUT_LISTENER_FEUK11UD = 30
LISTENER_FEUK11UD =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = HFE2PrePrdOra)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

ADR_BASE_LISTENER_FEUK11UD = /oracle/product