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John Watson's blog

Using reverse key indexes to solve buffer busy wait problems

Buffer busy wait and related events can cripple performance of concurrent inserts. Bad in a single instance database, far worse in a RAC (think "gc buffer busy"). Often the problem is because of a primary key populated from a sequence. Reversing the index can fix this problem.

Using hash clusters to solve buffer busy wait problems

Concurrent inserts into a table will often result in crippling buffer busy wait problems as sessions serialize on access to the last block(s) of the table segment. Using hash clusters can remove the issue.

Database 12c deferred global index maintenance

Many people are terrified of global indexes, one reason being that partition DDLs on the table will either render them unusable, or take forever as they are updated. Deferred global index maintenance solves this, and should be an important driver for the 12c upgrade.

Go native! PL/SQL native compilation

Why use interpreted PL/SQL when native compiled PL/SQL is so much faster? No reason at all - except that interpreted is the default, and most DBAs never change this. They should.

The COMMIT_WRITE parameter

Can this parameter really boost performance? This simple test suggests that it can.

Oracle 12c new feature: Unified Audit

Unified Audit is a major architectural change: fast, easy, and impossible for the DBA to bypass. On upgrade to Oracle 12c, you really should enable it. The earlier method that we all use is pretty awful.

12c SQL tuning: adaptive execution plans

The concept of an adaptive plan is that execution of a statement can start with one plan, and (during execution) switch to another. A pretty amazing capability. No need to run the statement to completion and try again: correct it in flight.

CTOUG re-launch meeting

I was at the Connecticut Oracle User Group re-launch meeting last week, talking about some of the 12c new features that I specially like: those related to what I call "the self-learning database".

Database 12c: automatic generation of extended statistics

Why does the CBO get it wrong? Often because it has insufficient information. No matter how often you analyze your tables, if your queries use multi-column predicates, the CBO will mis-calculate the cardinalities. You have to understand your data, and create extended statistics to correlate the columns. How many people do this? Hardly any. Not a problem any more: release 12c can do this for you. If you configure it appropriately.

Grid Infrastructure and RAC: the cluster interconnect

A necessary part of a cluster is the cluster interconnect: the private network between the cluster nodes. This component is critical for both reliability and scalability, and configuring it for fault tolerance and capacity is a matter of burning importance for the DBA and his System Administrator (not to mention the end users). One question is, should this be managed by the operating system or by Oracle?