Application continuity in Oracle RAC environments

Traditional enterprise databases such as banking and telecommunications are mostly based on Oracle Rac+dataguard's highly available architecture, and high-availability implementation and testing work is particularly important during the implementation of RAC projects due to the demanding business continuity requirements.

Oracle in the new version of the RAC Official document 12CR2 a separate chapter called ensuring application continuity, the degree of attention visible. In previous versions of oracle10g and 11g, the client implemented the RAC failover (failover) feature, various application applications and DB required various configuration adjustments, and these configuration steps became more streamlined as Oracle's new version of 12CR2 was coming.

The following is a brief summary of the failover configuration under the ORACLE11GR2 environment.

The client's connection is divided into connect time Connection Failover and runtime Connection Failover based on whether a pre-existing connection is used (such as a connection in the connection pool). The runtime prefix refers to a situation where a connection already exists, such as using a connection pool.

1. Connect Time Connection Failover

The configuration of the scan IP and service in the client's Tnsnames.ora can realize the failover when the database is connected;

2, Runtime Connection Failover

Oracle implements the runtime Connection Failover in two ways, TAF (Transparent application Failover) and FCF (Fast Connection failove R).

The first is TAF:

It can be defined in the connection string in the client side of the Tnsnames.ora, or it can be defined in server-side service. TAF is only valid for clients and connection pools using OCI connections, where the OCI connection can be encapsulated on the OCI connection, such as Jdbc-oci driver Support TAF, but JDBC thin driver does not support TAF (because the JDBC thin Dr Iver is not based on the OCI).

The second is FCF:

Fast Connection Failover, which is actually a client that is implemented by subscribing to the FAN HA events.

Because the JDBC thin connection is not based on the OCI, the Runtime Connection Failover in this case cannot use TAF, only FCF.

If you want the app app to have the TAF attribute, you can do a simple app makeover: first install the Oracle client in the client environment of the app, and then adjust the JDBC thin connection to the JDBC OCI connection.

In the ORACLE12CR2 version, failover can be based on transactions, and replay DML statements, with respect to 11g session-based, failover functionality has been greatly improved.

Application continuity in Oracle RAC environments