java.sql.sqlexception:ora-24778: Unable to open connection

WebLogic log: java.sql.sqlexception:ora-24778: Unable to open the connection. The analysis function is to have multiple operations on the remote table, and first look at the parameters about Db_link:

Sql> Show Parameter Open_links
NAME TYPE VALUE
------------------------------------ ----------- -------
Open_links Integer 4
Open_links_per_instance Integer 4

To restart the system after modifying the parameters:

Alter system set OPEN_LINKS=50 Scope=spfile;
Alter system set open_links_per_instance=255 Scope=spfile;

The official documents generally mean:

Open_links is the maximum number of open remote connections for a single session, including external stored procedures, external processes (something outside anyway). The default value is 4, the maximum value is 255, and when set to 0, no distributed transaction is indicated.

Open_links_per_instance is the maximum number of remote connections that an instance opens. The default value is 4 and the maximum is 4294967295, which is applied to the XA driver for JDBC, and open_links does not apply to the XA driver for JDBC.

I think open_links_per_instance size settings should be open_links several times, and in the new database should be clear, the late revision restart a bit depressed.

Open_links Property

	Description
Parameter type	Integer
Default value	4
Modifiable	No
Range of values	0 to 255

OPEN_LINKSSpecifies the maximum number of concurrent open connections to remote databases in one session. These connections include database links, as well as external procedures and cartridges, each of which uses a separate pro Cess.

Oracle counts one open link for the following:

• For each user this references a public or private database link

• For each external procedure or cartridge connection when it's executed for the first time

Both types of connections close when the session ends. You can also close a database link connection explicitly by issuing an ALTER SESSION CLOSE DATABASE LINK statement.

You should set this parameter to allow for the external procedure and cartridge connections expected during the session PL Us the number of databases referred to in typical distributed transactions (that's, a single SQL statement that reference s multiple databases), so then all the databases can is open to execute the statement. For example, if queries alternately Access databases A, B, and C, and are set to, time would be lost waiting whi OPEN_LINKS 2 Le one connection is broken and another made. Increase the value if many different databases is accessed over time.

This parameter refers-connections used for distributed transactions. Direct connections to a remote database specified as an application connects is not counted.

If you set OPEN_LINKS 0 to and then no distributed transactions is allowed.

Open_links_per_instance Property

	Description
Parameter type	Integer
Default value	4
Modifiable	No
Range of values	0 to 4294967295 (4 GB-1)
Real Application Clusters	Multiple instances can have different values.

OPEN_LINKS_PER_INSTANCESpecifies the maximum number of migratable open connections globally for each database instance. XA transactions use migratable open connections so, the connections be cached after a transaction is committed. Another transaction can use the connection, provided the user who created the connection's the same as the user who owns The transaction.

OPEN_LINKS_PER_INSTANCEis different from OPEN_LINKS , which indicates the number of connections from a session. The parameter is not a OPEN_LINKS applicable to XA applications.

java.sql.sqlexception:ora-24778: Unable to open connection