Identify how the network address information for Oracle Net Services can be stored in local files or in a centralized directory server. Using localized management, network address information is stored in
tnsnames.ora files on each computer in the network. Using centralized management, network address information is stored in centralized directory server.
The chapter contains the following topics:
When localized management is used, network computers are configured with the files described in Table 3-1. The files are stored locally on the computers.
Table 3-1 Oracle Net Configuration Files Used with Localized Management
Located on client and database server computers, this file may include the following:
Located on the database server, this configuration file for the listener may include the following:
Located on the computer where Oracle Connection Manager runs, this configuration file includes the following components:
Each Oracle Connection Manager configuration is encapsulated within a single name-value (NV) string, which consists of the preceding components.
Configuration files are typically created in the
ORACLE_HOME/network/admin directory. However, configuration files can be created in other directories. Oracle Net checks the other directories for the configuration files. For example, the order for checking the
tnsnames.ora file is as follows:
If the TNS_ADMIN environment variable is not set, then Oracle Net checks the
On Microsoft Windows, the TNS_ADMIN environment variable is used if it is set in the environment of the process. If the TNS_ADMIN environment variable is not defined in the environment, or the process is a service which does not have an environment, then Microsoft Windows scans the registry for a TNS_ADMIN parameter.
Oracle Database Global Data Services Concepts and Administration Guide for information about the
Operating system-specific documentation
When an Oracle network uses a directory server, the directory server manages global database links as network service names for the Oracle databases in the network. Users and programs can use a global link to access objects in the corresponding database.
Oracle Net Services uses a centralized directory server as one of the primary methods for storing connect identifiers. Clients use the connect identifiers in their connect string, and the directory server resolves the connect identifier to a connect descriptor that is passed back to the client. This feature is called directory naming. This type of infrastructure reduces the cost of managing and configuring resources in a network.
Oracle Internet Directory provides a centralized mechanism for managing and configuring a distributed Oracle network. The directory server can replace client-side and server-side localized
Figure 3-1 shows a client resolving a connect identifier through a directory server.
The client contacts the directory server to resolve a connect identifier to a connect descriptor.
The directory server resolves the connect identifier and retrieves the connect descriptor for the client.
The client sends the connection request to the listener, using the connect descriptor.
Figure 3-1 Client Using a Directory Server to Resolve a Connect Identifier
This section contains the following topics:
Directory servers store information in a hierarchical namespace structure called a directory information tree (DIT). Each node in the tree is called an entry. Oracle Net Services uses both the tree structure and specific entries in the tree. DITs are commonly aligned with an existing domain structure such as a Domain Name System (DNS) structure or a geographic and organization structure.
Figure 3-2 shows a DIT structured according to DNS domain components.
Figure 3-2 DNS Domain Component DIT
Figure 3-3 shows a DIT structured according to country, organization, and organizational units. This structure is commonly referred to as an X.500 DIT.
Figure 3-3 X.500 DIT
For example, consider Figure 3-4. The
cn=db1 entries represent a network service name and a database service, respectively. Additional entries under
cn=db1 contain the connect descriptor information. These entries are not represented in the graphic. The
cn=db1 entries enable clients to connect to the database using connect strings
Figure 3-4 Database Service and Net Service Entries in a DIT
Each entry is uniquely identified by a distinguished name (DN). The DN indicates exactly where the entry resides in the directory server hierarchy. The DN for db1 is
dn:cn=db1,cn=OracleContext,dc=jp,dc=example,dc=com. The DN for sales is
dn:cn=sales,cn=OracleContext,dc=jp,dc=example,dc=com. The format of a DN places the lowest component of the DIT to the left, then moves progressively up the DIT.
Each DN is made up of a sequence of relative distinguished names (RDNs). The RDN consists of an attribute, such as
cn, and a value, such as
sales. The RDN for db1 is
cn=db1, and the RDN for sales is
cn=sales. The attribute and its value uniquely identify the entry.
For domain component namespaces, the default directory entry defined for the client must be in one of the following formats:
In the preceding syntax, [dc] represents an optional domain component, [...] represents additional domain component entries and ou represents the organizational unit entry.
The fully-qualified name used in the connect identifier by the client must be in one of the following formats:
In the preceding syntax, [cn] represents the Oracle Net entry.
Example 3-1 Using a Fully-Qualified Name with an Organizational Unit
Consider a directory server that contains an entry for database object sales with a DN of
cn=sales,cn=OracleContext,dc=jp,dc=example,dc=com. In this example, the client requires a connect identifier of
Consider a similar entry that contains database object sales with a DN of
Because domain components must be separated from organization units, the client must use the format
email@example.com. The client requires the connect identifier to be
Figure 3-5 illustrates the preceding example.
Figure 3-5 Fully-Qualified Name for Domain Component Namespaces
For X.500 namespaces, the default directory entry defined for the client must be in one of the following formats:
In the preceding formats, [ou] represents an optional organizational unit name, o represents the organization, and c represents the country.
The fully-qualified name the client uses as the connect identifier must be in one of the following formats:
In the preceding formats, cn represents the Oracle Net entry.
For example, if the directory contains database object
sales with a DN of
cn=sales,cn=OracleContext,ou=mktg,o=example,c=jp, then the client requires a connect identifier of
sales.mktg.example.jp. Figure 3-6 illustrates this example.
Figure 3-6 Fully-Qualified Name for X.500 Namespaces
If a client is configured with a default realm Oracle Context, then an entry can be identified by its relative name, and the service can be referred to by its common name. A relative name can be used if the entry is in the same Oracle Context that was configured to be the default Oracle Context for the client's Oracle home.
Consider a directory server that contains an entry for a database called sales with a DN of
dn:cn=sales,cn=OracleContext,o=example,c=us, as shown in Figure 3-7. If the client is configured with a default realm Oracle Context of
cn=OracleContext,o=example,c=us, then the connect identifier can simply be
Figure 3-7 Relative Naming
Oracle Fusion Middleware Administrator's Guide for Oracle Internet Directory for additional information about how clients locate a directory
Oracle Database JDBC Developer's Guide for additional information about JDBC drivers
Consider the same directory structure as shown in Figure 3-7, but with the client's Oracle home configured with a default realm Oracle Context of
Because the client is configured with a default Oracle Context that does not match the location of sales in the directory server, a connect string that uses sales does not work. Instead, the client must specifically identify the location of sales, which can be done using one of the following ways:
The entry's complete DN can be used in the connect string, for example:
CONNECT username@"cn=sales,cn=OracleContext,o=example,c=us" Enter password: password
The entry can be referred to by a fully-qualified DNS-style name which is mapped by the Directory Naming adapter to the full x.500 DN of the database object in the LDAP directory, for example:
CONNECT firstname.lastname@example.org Enter password: password
In Figure 3-8, the entries
sales reside under
cn=OracleContext. This entry is a special RDN called an Oracle Context. The entries under Oracle Context support various directory-enabled features, including directory naming.
Figure 3-8 Oracle Context in the DIT
During directory configuration, you set the default Oracle Context. Clients use this Oracle Context as the default location to look up connect identifiers in the directory server. With Oracle Internet Directory, an Oracle Context located at the root of the DIT, with DN of
dn:cn=OracleContext, points to a default Oracle Context in an identity management realm. An identity management realm is a collection of identities governed by the same administrative policies. This Oracle Context is referred to as a realm Oracle Context. Unless configured to use another Oracle Context, clients use this realm-specific Oracle Context.
The default Oracle Context affects the connect string. For example, if a client must access the
sales entry frequently, then a reasonable default Oracle Context would be
dc=jp,dc=example,dc=com. If a client directory entry does not match the directory entry where a service is located, then the client must specify the fully-qualified name of an entry in the connect string, as described in "Client Connections Using Directory Naming".
cn=OracleContext does not have to be explicitly specified in the connect string.
Oracle Fusion Middleware Administrator's Guide for Oracle Internet Directory for additional information about an identity management realm
Directory naming enables you to create network service alias entries in addition to database service and network service name entries. A network service alias is an alternative name for a network service name or database service. A network service alias entry does not have connect descriptor information. Instead, it references the location of the entry for which it is an alias. When a client requests a directory lookup of a network service alias, the directory determines that the entry is a network service alias and completes the lookup as if it is the referenced entry. For example, in Figure 3-9, a network service alias of db1alias is created for a database service of db1. When db1alias is used to connect to a database service, as in
@db1alias, it will actually resolve to and use the connect descriptor information for db1.
Figure 3-9 Net Service Alias db1alias in a Directory Server
There are several uses for network service aliases. As shown in Figure 3-9, a network service alias can be useful as a way for clients to refer to a network service name by another name. Another use is to have a network service alias in one Oracle Context for a database service or network service name in a different Oracle Context. This enables a database service or network service name to be defined once in the directory server, but referred to by clients that use other Oracle Contexts.
In Figure 3-10, database service db1 resides in
dc=jp,dc=example,dc=com. A network service alias named db1 is created in
dc=us,dc=example,dc=com. This enables clients in both Japan and the United States to use the connect string
@db1 as opposed to clients in the Unites States needing to specify
Figure 3-10 Net Service Alias db1 in a Directory Server
The database service entries are configured during or after installation. You can then use Oracle Enterprise Manager Cloud Control or Oracle Net Manager to modify the Oracle Net attributes of the database service entries. You can also use these tools to create network service name and network service alias entries.
To use these configuration tools, a DIT structure containing a root Oracle Context, and identity management realm must exist. The directory administrator creates this structure with Oracle Internet Directory Configuration Assistant. For some deployments, the directory administrator may need to create additional Oracle Contexts. Additional Oracle Contexts are usually used to subdivide large sites, or separate a production environment from a test environment.
Certain tools are used by certain groups, and you must be a member of the group to use the tools, as described in the following:
To create a database service entry with Database Configuration Assistant:
To create network service names or network service aliases with Oracle Net Manager:
OracleNetAdmins group is owned by itself. Members of the
OracleNetAdmins group have create, modify, and read access to Oracle Net objects and attributes. They can also add or delete members in the group, and add or delete groups to be owners of the
Any member of the
OracleNetAdmins group can add or delete other members from the
OracleNetAdmins group. If you prefer another group to add or delete
OracleNetAdmins members, then you can change the owner attribute of the
OracleNetAdmins group to another group. The owner cannot be an individual user entry but must be a group entry, and the group entry is one comprised of the LDAP schema object classes
OracleContextAdmins group is a super-user group for Oracle Context. Members of the
OracleContextAdmins group can add all supported types of entries to Oracle Context.
The directory user that created Oracle Context is automatically added to these groups. Other users can be added to these groups by the directory administrator.
Most clients needing to perform name lookups in the directory server access the directory server using anonymous authentication. To perform a lookup, the directory server must allow anonymous authentication. Directory servers usually allow anonymous authentication by default, however, some directory servers, such as earlier releases of Oracle Internet Directory, require directory configuration to allow anonymous access.
To look up entries, a client must be able to find the directory server in which that entry resides. Clients locate a directory server in one of two ways:
Dynamically using DNS. In this case, the directory server location information is stored and managed in a central domain name server. The client, at request processing time, retrieves this information from DNS.
Statically in the directory server usage file,
ldap.ora, created by Oracle Internet Directory Configuration Assistant and stored on the client host.
After a directory is found, clients are directed to the realm Oracle Context from the root Oracle Context.
Clients make connections to a database using connect identifiers in the same way they might use other naming methods. A connect identifier can be a database service, network service name, or network service alias. These can be referred to by their common names (relative name) if the default Oracle Context is where the entity resides. If not, then the connect identifier needs a fully-qualified name or distinguished name.
Microsoft Active Directory documentation
The following considerations should be reviewed when using directory servers:
Connect identifiers are stored in a directory server for all clients to access. Depending on the number of clients, there can be a significant load on a directory server.
During a connect identifier lookup, a name is searched under a specific Oracle Context. Users expect relatively quick performance so the database connect time is not affected. Because of the scope of the lookup, users may begin to notice slow connect times if lookups take more than one second.
You can resolve performance problems by changing the network topology or implementing replication.
Directory server vendor documentation for details on resolving performance issues
Administrative clients can create and modify entries in the directory server, so security is essential. This section contains the following security-related topics:
Clients use different methods of authentication depending upon the task that is to be performed.
Clients that perform lookups for information in the directory server typically use anonymous authentication. In Oracle Database 12c, it is possible to configure clients to authenticate their LDAP bind during name lookup. Sites that need to protect their network service data or disable anonymous binds to the directory must configure their clients to use wallets to authenticate during name lookup. These clients require setting the following two parameters in the
names.ldap_authenticate_bind = TRUE wallet_location = location_value
Clients that administer the directory server entries authenticate with the directory server. Database Configuration Assistant or Oracle Net Manager can be used to add or modify the entries. Only authenticated users with proper privileges can modify entries. Use one of the following authentication methods:
The client identifies itself to the directory server by means of a DN and a password. The server verifies that the DN and password sent by the client matches the DN and password stored in the directory server.
The client identifies itself to the directory server by means of a public-key encryption available with Secure Sockets Layer (SSL). In public-key encryption, the sender of a message encrypts the message with the public key of the recipient. Upon delivery, the recipient decrypts the message using the recipient's private key.
Authentication is used with access control lists (ACLs) to determine whether clients can read, modify, or add information in the directory server. ACLs specify the following:
The entries that the user can access.
The authentication method used to access the entry.
The access rights, or what the user can do with the object, such as read or write.
ACLs are established for a group of users. During Oracle Context creation, the
OracleContextAdmins groups are created.
The user who creates Oracle Context using Oracle Net Configuration Assistant is automatically added as the first member of these groups.
Table 3-2 describes ACL requirements for these groups, anonymous users, and their relation to Oracle Net entries in the directory server.
Table 3-2 ACL Requirements for User Groups
All Oracle Net attributes and objects in the directory server have read access for the anonymous user. Read access of these objects for anonymous is also applied to Oracle Context. This enables anonymous users to browse directory naming entries contained within the
Oracle Net Configuration Assistant sets up this access during client installation.
In addition to the Oracle Context creator, other users can be added to this group by the directory administrator using Oracle Enterprise Manager Cloud Control.
In addition to the Oracle Context creator, other users can be added to this group by the directory administrator with Oracle Enterprise Manager Cloud Control.
In addition to the Oracle Context creator, other users can be added to this group by the directory administrator.
Situations in which a high degree of security is desired for lookup or read-access to Oracle Net Services name and related data, administrators can define additional read-access control for some or all of the data. Such ACL definitions can prevent anonymous users from reading the Oracle Net Services data. If read-access to Oracle Net Services data is restricted, then clients must use authenticated binds to do name lookups.
There are no predefined groups or procedures for the Oracle configuration tools for defining read-access restrictions on this data, so administrators must use standard object management tools from their directory system to manually create any necessary groups and ACLs.
ACLs can be added to Oracle Net Services objects using
ldapmodify and an LDIF-format file. Example 3-2 shows how to restrict all access for user,
Example 3-2 Restricting User Access with an Access Control List
dn: cn=sales,cn=oraclecontext,dc=example,dc=com replace: orclentrylevelaci orclentrylevelaci: access to attr=(*) by dn="cn=user1" (noread,nosearch,nowrite,nocompare)
The preceding example illustrates the basic form of an ACL for a single object. This approach is not necessarily the best way to define access because access definitions for objects are complex and may involve security properties which are inherited from parent nodes in the DIT. Oracle recommends that administrators refer to the documentation for their directory systems, and integrate access management for Oracle Net Services objects into a directory-wide policy and security implementation.
For Oracle Internet Directory directories,
oidadmin has functionality to create users, groups, and also define ACLs for objects and general directory security.
Documentation from your directory server vendor for information about how to set ACLs on directory entry
"Authentication Methods" for information about configuring clients to use authenticated binds for name lookup
"About the OracleNetAdmins Group" for information about adding users to the
Directories must be populated with the correct version of the Oracle schema before Oracle Context, a database service or network service name entry can be created. The Oracle schema defines the type of objects, called object classes, that can be stored in the directory server and their attributes. Table 3-3 lists the object classes for database service, network service name, and network service alias entries.
Table 3-3 Oracle Net Services LDAP Main Object Classes
Defines the attributes for database service entries.
Defines the attributes for network service name entries.
Defines the attributes for network service alias entries.
Table 3-4 lists the object classes used by
Table 3-4 Oracle Net Services LDAP Derived Object Classes
Defines a listener protocol address.
Defines a list of addresses.
Specifies a connect descriptor containing the protocol address of the database and the connect information to the service.
Defines a list of connect descriptors.
These object classes use attributes that specify the contents of connect descriptors.
Oracle Database Net Services Reference for additional information about these object classes and their attributes
In addition to Oracle Internet Directory, directory naming support is also provided with Microsoft Active Directory with the following limitations:
Oracle provides support for Microsoft Active Directory only on Microsoft Windows operating systems. Therefore, client computers and the database server must run on Microsoft Windows operating systems to access or create entries in Microsoft Active Directory.
The following features are not supported by Microsoft Active Directory:
Multiple Oracle Contexts
Microsoft Active Directory can support only one Oracle Context.
Net service aliases
You cannot create network service aliases in Microsoft Active Directory. However, you can create network service names.
Microsoft Active Directory documentation for Microsoft-specific information