For example, if the database link appears inside procedure scott.p (created by scott), and user jane calls procedure scott.p, then the current user is scott. When executing a stored object (such as a procedure, view, or trigger) that initiates a database link, CURRENT_USER is the name of the user that owns the stored object, and not the name of the user that called the object. If the database link is used directly rather than from within a stored object, then the current user is the same as the connected user. The current user must be a global user with a valid account on the remote database. Specify CURRENT_USER to create a current user database link. The CONNECT TO clause lets you specify the user and credentials, if any, to be used to connect to the remote database. Periods are permitted in names of database links, so Oracle Database interprets the entire name, such as ralph.linktosales, as the name of a database link in your schema rather than as a database link named linktosales in the schema ralph. You cannot create a database link in another user's schema, and you cannot qualify dblink with the name of a schema. The maximum number of database links that can be open in one session or one instance of an Oracle RAC configuration depends on the value of the OPEN_LINKS and OPEN_LINKS_PER_INSTANCE initialization parameters. If the value of GLOBAL_NAMES is FALSE, and if you have changed the global name of the database, then you can specify the global name. If the value of the GLOBAL_NAMES initialization parameter is TRUE, then the database link must have the same name as the database to which it connects. If you specify the database name as a quoted identifier, then the quotation marks are silently ignored. The database link name is case insensitive and is stored in uppercase ASCII characters. If you specify only the database name, then Oracle Database implicitly appends the database domain of the local database. Specify the complete or partial name of the database link. To prevent an unauthorized session from attempting to connect through the database link, when you specify SHARED you must also specify the dblink_authentication clause for the users authorized to use the database link. Once a session is established on the target database, that session is disassociated from the connection, to make the connection available to another session on the source database. In a shared database link, multiple sessions in the source database share the same connection to the target database. However, a shared private database link can be useful when many clients access the same local schema, and therefore use the same private database link. Shared links are typically also public database links. In a shared server configuration, shared database links can keep the number of connections into the remote database from becoming too large. Specify SHARED to create a database link that can be shared by multiple sessions using a single network connection from the source database to the target database.
0 kommentar(er)
