In a Nutshell


I/O operations are a necessity of every process that reads from or writes to the database. Database reads and writes are simple on the surface, but the path between the database and the physical disks can be a convoluted mess of software and hardware from various manufacturers, each with its own limitations. With all the handshakes that have to take place, it is a miracle that you get your data accurately! Although a DBA is not required to know the hardware layer intimately, a good knowledge of the system will definitely help you better manage the database and enrich your database administration experience.

In this chapter, we covered seven common I/O related wait events: db file sequential read, db file scattered read, direct path read, direct path write, log file parallel write, db file parallel write, and controlfile parallel write . The first four events are normally indicative of problems within the application. As such, the cure should come from the application and not the database.

The type of I/O operation (synchronous or asynchronous) makes a difference in I/O performance. Asynchronous I/O is not always faster and it may not be supported on your platform. You must choose the I/O operation that is right for your platform.




Oracle Wait Interface
Oracle Wait Interface: A Practical Guide to Performance Diagnostics & Tuning (Osborne ORACLE Press Series)
ISBN: 007222729X
EAN: 2147483647
Year: 2004
Pages: 114

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