Using WebLogic Server With Oracle RAC(轉)

Oracle RAC Scalability with WebLogic Server

You can add nodes to the cluster easily and there is no need to partition data when you add them. This means that you can horizontally scale the database tier as usage and demand grows by adding RAC nodes, storage, or both. You can then scale WebLogic Server by adding a connection pool that maps to the new node.

Oracle RAC Availability with WebLogic Server

Note that Oracle RAC does not provide failover for database connections; nor does WebLogic Server. But transactions are failed over in the sense that they are heuristically driven to completion, based on the time of the failure.

資料庫連線不提供failover功能，但事務可以被failover。

Oracle RAC Load Balancing with WebLogic Server

If your application requires load balancing across RAC nodes when using global transactions (XA), BEA supports this capability through use of JDBC MultiPools with Oracle RAC nodes.

In a configuration without a MultiPool, WebLogic Server relies on the connect-time failover feature provided by the Oracle Thin driver to work with Oracle RAC. As described in Oracle's Technical Note 235118.1, the Oracle Thin driver cannot guarantee that a transaction is initiated and concluded on the same Oracle RAC instance when the driver is configured for load balancing. As Oracle RAC requires that all database operations inside a global transaction be routed to the same Oracle instance, this known limitation means that you cannot use driver-level load balancing when using XA with Oracle RAC and therefore you cannot use a primary/primary RAC configuration.

不用多池就需要靠Oracle Thin driver來實現failover，但不能負載均衡XA事務。

Oracle RAC Failover with WebLogic Server

Although Oracle RAC offers JDBC connect-time failover features, for most configurations, BEA recommends using WebLogic JDBC MultiPools to handle failover instead.

Note: Transparent Application Failover (TAF) requires the use of the Oracle OCI driver. Because BEA requires the use of the Oracle Thin driver, TAF is not supported.

BEA推薦用WebLogic JDBC多池來實現failover。

Configuring the Listener Process for Each Oracle RAC Instance

For Oracle RAC, the listener process establishes a communication pathway between a user process and an Oracle instance. When you use Oracle RAC with WebLogic Server, the user process is typically a JDBC connection pool.

When a connection pool is created, it attempts to create a pool of database connections for applications to borrow. If a pooled database connection becomes inoperative or if the connection pool is configured to grow in capacity, the connection pool attempts to create additional database connections up to the maximum specified in the configuration file. In all of these instances, the Oracle listener process handles the connection request on the Oracle RAC instance.

為了實現負載均衡，連線池的初始值和最大值不能相同。

Choosing a WebLogic Server Configuration for Use with Oracle RAC

To connect to multiple Oracle 9i RAC or Oracle 10g RAC instances when using global transactions (XA), BEA recommends the use of transaction-aware WebLogic JDBC MultiPools, which support failover and load balancing, to connect to the RAC nodes. For more information see Using MultiPools with Global Transactions. You must either Weblogic Server 8.1 SP5 or later or have WebLogic Server 8.1 SP4 with the Oracle 10g RAC patch installed for this configuration. The WebLogic Server 8.1 SP4 Oracle 10g RAC patch is available at http://dev2dev.bea.com/wlserver/patch/wls81sp4_MP_OracleRAC_patch.html

當用全域性事務（XA）時，為了連線到Oracle 9i RAC或者Oracle 10g RAC例項，BEA推薦使用WebLogic JDBC多池進行事務處理，你必須具有Weblogic Server 8.1 SP5或更高版本，或者WebLogic Server 8.1 SP4具有Oracle 10g RAC補丁。

WebLogic Server 8.1 SP5 is certified to support Multipools with XA only on Oracle RAC

WebLogic Server 8.1 SP5被鑑定僅僅在Oracle RAC中可支援具有全域性事務的多池

在WebLogic Cluster＋Oracle RAC系統中，需要考慮如下限制：

Required JDBC Driver Configuration for Use with XA

In this configuration, you must use the Oracle Thin driver connect-time failover to create database connections

Oracle 9i RAC XA Requirements

       全域性事務必須被初始化、準備、終止在RAC的同一個例項上。

       在RAC中，全域性事務必須有相同的事務ID。

在WebLogic Cluster和Oracle RAC的系統中，存在以下潛在風險：

1、 在某些情況下，資料會丟失，如網路中斷

2、 在某些特定的情況下，會發生資料死鎖。

3、 在某些特定的情況下，事務處理順序發生變化。

§                        The Oracle Thin Driver 10g and Oracle Thin/XA Driver 10g are the default drivers for WebLogic Platform. 8.1 SP3.

WebLogic Platform. 8.1 SP3預設的驅動是Oracle Thin Driver 10g和Oracle Thin/XA Driver 10g