Two Ways to Connect to Remote Oracle Databases

Oracle Network Services — also known as Oracle Net, and formerly known as SQL*Net — provides two primary methods for connecting client applications to remote Oracle databases. Both methods have existed since Oracle 9i and remain the standard connection approaches through Oracle 23ai. The choice between them determines how much client-side configuration is required, how complex the connection descriptor can be, and how well the connection supports enterprise features such as load balancing, failover, and multi-address configurations.

The original SQL*Net version 1 connection model required clients to embed the full protocol, hostname, and database name in every connection request — for example, sqlplus /@t:host:database where t indicated TCP/IP, host was the remote server name, and database was the Oracle SID. This approach was functional but inflexible — changing a server hostname required updating every application that embedded the connection string. SQL*Net version 2 introduced the tnsnames.ora alias lookup that separated the connection identifier from the connection details. Oracle 9i and later formalized and extended both approaches into the two methods that Oracle Net uses today.

Method 1 — Easy Connect Naming Method (EZCONNECT)

The Easy Connect Naming Method is the simplest approach to Oracle database connectivity. It requires no client-side configuration files, no tnsnames.ora entry, and no additional naming resolution setup. Oracle Net directly interprets the connection string provided in the connect identifier and resolves the connection without any lookup step.

Easy Connect is enabled by default in modern Oracle clients and is the recommended method for simple TCP/IP connections, development environments, ad-hoc administrative connections, and any scenario where minimizing client configuration overhead is a priority.

Easy Connect Syntax

The basic Easy Connect syntax is:

username/password@host[:port][/service_name]

The host is the hostname or IP address of the remote database server. The port defaults to 1521 if omitted. The service_name is the Oracle database service name — equivalent to the SERVICE_NAME parameter in a tnsnames.ora CONNECT_DATA block.

Practical examples:

-- Basic Easy Connect with explicit port and service name
sqlplus hr/password@dbhost.example.com:1521/orclpdb

-- Port defaults to 1521 when omitted
sqlplus hr/password@192.168.1.100/orclpdb

-- Oracle 23ai TCPS connection with SSL
sqlplus hr/password@'tcps://dbhost.example.com:2484/orclpdb'

-- Oracle 23ai example from production
sqlplus system/PassFun23ai@'mmfalcon:1521/mmdb23ai'

Easy Connect Plus — Oracle 19c and 23ai Enhancements

Oracle 19c introduced Easy Connect Plus, which extends the basic Easy Connect syntax to support additional connection parameters directly in the connection string without requiring a tnsnames.ora entry. Easy Connect Plus supports:

• Server type specification: DEDICATED or SHARED server mode inline in the connect string
• SSL/TLS parameters: ssl_server_dn_match, ssl_server_cert_dn for TCPS connections
• Connection timeout: connect_timeout and retry_count parameters
• ADDRESS_LIST grouping: Multiple addresses for basic failover directly in the Easy Connect string without a tnsnames.ora descriptor

-- Easy Connect Plus with TCPS and SSL verification in Oracle 23ai
sqlplus hr/password@'tcps://sales-server:2484/sales_pdb?ssl_server_dn_match=yes'

-- Easy Connect Plus with connection timeout
sqlplus hr/password@'dbhost:1521/orclpdb?connect_timeout=10&retry_count=3'

In Oracle 23ai, Easy Connect Plus also supports LDAP/LDAPS parameters and can reference Centralized Configuration Providers in OCI Object Storage — making it practical for cloud and hybrid environments without any local configuration file dependency.

Easy Connect Advantages and Limitations

Easy Connect is ideal for: development and testing environments where configuration simplicity is valued over enterprise features; ad-hoc DBA connections to remote databases; simple application deployments with a single database endpoint; and container-based Oracle deployments where client configuration file management is undesirable.

Easy Connect is less suitable for: Oracle RAC environments requiring client load balancing across multiple instances; configurations requiring connect-time failover across multiple listener addresses; and legacy application drivers that do not support the Easy Connect Plus extended syntax introduced in Oracle 19c.

Method 2 — Local Naming Method (tnsnames.ora)

The Local Naming Method uses a network service name alias defined in the client's tnsnames.ora configuration file. The alias maps to a full connection descriptor containing the protocol, host address, port, and database service name. The client application connects using only the short alias — Oracle Net resolves the alias to the full connection descriptor transparently.

The tnsnames.ora file is located in $ORACLE_HOME/network/admin/ on the client machine, or in the directory specified by the TNS_ADMIN environment variable. In Oracle 23ai, the TNS_ADMIN variable can point to an OCI Object Storage location through Centralized Configuration Providers, eliminating the need for a local file.

Local Naming Syntax

A tnsnames.ora entry for a remote database:

MY_REMOTE_DB =
  (DESCRIPTION =
    (ADDRESS =
      (PROTOCOL = TCP)
      (HOST     = sales-server)
      (PORT     = 1521))
    (CONNECT_DATA =
      (SERVER       = DEDICATED)
      (SERVICE_NAME = sales.us.example.com)))

Once the alias is defined in tnsnames.ora, connecting to the remote database requires only the alias name:

-- Local naming connection using tnsnames.ora alias
sqlplus hr/password@MY_REMOTE_DB

-- Oracle 23ai example
sqlplus system/PassFun23ai@mmdb23ai

The SERVICE_NAME parameter in the CONNECT_DATA block is the modern standard — it replaced the legacy SID parameter introduced in Oracle 8.1 and earlier. Use SERVICE_NAME for all Oracle 9i and later connections.

Local Naming for RAC and Failover Configurations

The Local Naming Method's primary advantage over Easy Connect is its support for complex multi-address configurations — particularly Oracle RAC load balancing and connect-time failover. A single tnsnames.ora alias can specify multiple listener addresses:

SALES_RAC =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (LOAD_BALANCE = ON)
      (FAILOVER     = ON)
      (ADDRESS = (PROTOCOL = TCP)(HOST = rac-node1)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = rac-node2)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = rac-node3)(PORT = 1521)))
    (CONNECT_DATA =
      (SERVICE_NAME = sales.us.example.com)
      (SERVER       = DEDICATED)))

With LOAD_BALANCE = ON, Oracle Net randomly selects from the available addresses at connect time, distributing new connections across all three RAC nodes. With FAILOVER = ON, if one address is unavailable, Oracle Net automatically tries the next address in the list — providing connect-time failover without application code changes.

Local Naming Advantages and Limitations

Local Naming is preferred for: Oracle RAC environments requiring client-side load balancing; configurations requiring connect-time failover across multiple listeners; enterprise deployments where centralized tnsnames.ora distribution provides consistent connection management; and database links where the USING clause references a TNS alias.

Local Naming requires maintaining tnsnames.ora files on client machines — historically one of the most significant Oracle DBA operational burdens in large deployments. Oracle 23ai addresses this through Centralized Configuration Providers, which store tnsnames.ora content as JSON in OCI Object Storage, making it available to all clients without local file distribution.

Controlling Naming Method Resolution Order

The sqlnet.ora file controls which naming methods Oracle Net tries and in which order when resolving a connect identifier. The NAMES.DIRECTORY_PATH parameter specifies the resolution sequence:

-- sqlnet.ora — naming method resolution order
NAMES.DIRECTORY_PATH = (TNSNAMES, EZCONNECT)

With this configuration, Oracle Net first checks tnsnames.ora for the connect identifier. If not found, it attempts Easy Connect interpretation. The order can be reversed or extended to include LDAP directory naming:

-- sqlnet.ora — include LDAP directory naming
NAMES.DIRECTORY_PATH = (LDAP, TNSNAMES, EZCONNECT)

In Oracle 23ai, Centralized Configuration Providers are added to the resolution path through the CONFIG_FILE parameter, allowing the client to retrieve connection descriptors from OCI Object Storage as a fourth resolution method alongside the three traditional options.

Comparison — Easy Connect vs Local Naming

Summary

Oracle Network Services provides two primary methods for connecting to remote databases. Easy Connect (EZCONNECT) requires no client-side configuration — the host, port, and service name are embedded directly in the connect string, making it ideal for simple environments and development work. Easy Connect Plus in Oracle 19c and 23ai extends this with TCPS/TLS parameters, connection timeouts, and retry configuration inline. The Local Naming Method uses a tnsnames.ora alias that Oracle Net resolves to a full connection descriptor, supporting complex RAC, failover, and multi-address configurations that Easy Connect cannot handle without extensions. Both methods connect through the Oracle Net Foundation Layer to the Oracle Net Listener and ultimately to the Oracle Database. The sqlnet.ora NAMES.DIRECTORY_PATH parameter controls which method Oracle Net tries first when a connect identifier is submitted. The next lesson examines the features of Oracle Net Services and the UPI/OPI programmatic interface architecture.

Oracle TNS Quiz