Article

Don Burleson answers your Oracle availability questions

Tim DiChiara

On July 23, 2002, Don Burleson of BEI Oracle Consulting gave an excellent Webcast on SearchDatabase titled Using Oracle9i RAC and TAF for continuous availability

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. (Click the link to hear the complete presentation.) Here are answers to audience questions that Don didn't have time to address.

Larry says that applications do not longer have to be 'RAC-aware,' as was the case with OPS. Do you have any experience that shows that this is more or less true?

In a sense, yes. The applications must connect to a specific OPS/RAC node at connect time, but to the app, RAC looks like any other database. However, if we add TAF, then no, the application must be TAF-aware.

Are there Intel/Linux implementations of RAC and how are they performing?

Yes, RAC is available for MS-Windows, but RAC is generally used by large-scale UNIX platforms.

But the Distributed Lock Manager still exists. It just has a new name global cache serves. The block now doesn't ping on disks but still pings between buffercaches. So don't you need to partition your application to avoid this cache ping?

Good question! The "ping" is now softer because all data buffer contents are in the same. However, you should still partition each node according to the data access patterns to reduce pinging.

Can you elaborate on the TAF incompatibility with Forms? Specifically, is the session lost entirely, or just the current transaction?

As I understand it, the session failover will happen, but the SQL in the transaction is lost. See Metalink for details.

Re phrase of previous question: On disk failure of the physical disk failure was on an operating system disk in a node of RAC, would this condition affect the rest of the nodes in RAC?

It depends on which data file is hammered. If you lose the data dictionary file, all nodes might crash, but if you loose a user data file, then only that tablespaces will be taken offline, with the node still active.

Does RAC uses OPS or is it replacing OPS?

RAC is the latest incarnation of OPS, and the product was re-named from OPS to RAC.

Are utilities run in parallel across multiple servers with RAC. For example does load only use one servers CPU or can it run across both instances in a 2 node RAC cluster.

No, any single transaction is assigned to only one node. However, each RAC node may have many CPUs, so intra-node parallelism is possible.

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