Database Reference
In-Depth Information
Unix process pid: 3196, image:
oracle@oel6rac1.example.com
(LREG)
...
Services:
...
2 -
po.example.com
flg=0x4, upd=0x6
goodnes=0, delta=1
...
Listen Endpoints:
0 -(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(
HOST=oel6rac1.example.com
)
(PORT=5500))
(Presentation=HTTP)(Session=RAW))
flg=0x80000000, nse=0, lsnr=, lflg=0x13
pre=HTTP, sta=0
If a service is not registered properly to the listeners or if the service quality decisions taken by the listeners are
incorrect, then you can trace the service registration to check if the listeners received correct service metrics.
Version 11.2 introduces the Valid Node Checking for Registration feature. SCAN listeners will accept registration
from any IP address in the same subnet as the SCAN IP address. The VIP listener will accept the registration only from
the local node. You can use invited_nodes to specify the permitted nodes for listener registration.
Runtime Failover
At runtime, a connection can be configured to fail over quickly to an available instance by configuring the failover
type service attribute. A service supports failover types of NONE, SESSION, or SELECT. Failover type NONE does not
provide any failover. If the failover type is set to SESSION, then after a node failure, sessions will fail over to surviving
instances and the application must restart all work, including in-transit work. If the failover type is SELECT, then
cursor fetch details are remembered by the client-side JDBC/OCI driver, the SELECT statement is restarted, and
FETCH continues from the last row fetched before the failure.
In version 11.2, while the SELECT failover type supports a transparent restart of queries, it doesn't restart any
DML operation. The application must restart DML statements, and failures in DML statements must be handled by
the application.
Version 12c introduces
TRANSACTION
, a new failover type, and this failovertype attribute value is specific to a
new feature called Application Continuity. Application Continuity also captures DML changes and replays the DML
activity using the Oracle client-side replay driver. The Application Continuity feature is discussed later in this chapter.
In version 12c, command options are specified more verbally. For example, in 11.2, option -e specifies the
failover type, and in version 12c, service attribute
failovertype
specifies failover type.
Service in Second Network
A service can be configured to operate in a subnet. For example, to specify a service to be available in only the second
network, you would specify option -k 2 while creating a service. In version 12c, clause -netnum 2 can be used to
specify that the service will operate only in the second network. Please refer to Chapter 9 to learn more about the
second network in a RAC cluster.
