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Database Configuration and I/O Issues

After completing this lesson, you should be able to do the following: List the advantages of distributing different Oracle file types Diagnose tablespace usage problems List reasons for partitioning data in tablespaces Describe how checkpoints work Monitor and tune checkpoints Monitor and tune redo logs | Database Configuration and I/O Issues Objectives After completing this lesson, you should be able to do the following: List the advantages of distributing different Oracle file types Diagnose tablespace usage problems List reasons for partitioning data in tablespaces Describe how checkpoints work Monitor and tune checkpoints Monitor and tune redo logs Oracle Processes and Files Process Oracle file I/O Data files Log Archive Control CKPT Read/Write Read/Write DBWn Write LGWR Write Read/Write ARCn Read Write Read/Write SERVER Read/write Read Write Read/Write Oracle Processes and Files Whereas most server processes only read from disk, sort direct write server processes write to disk. The CKPT process only accesses the data file headers; the DBWn process writes out the actual table data. The server process reads the redo logs, writes to the archive logs, and read/writes to the control file under certain backup and recovery operations. For example, when performing manual archiving the | Database Configuration and I/O Issues Objectives After completing this lesson, you should be able to do the following: List the advantages of distributing different Oracle file types Diagnose tablespace usage problems List reasons for partitioning data in tablespaces Describe how checkpoints work Monitor and tune checkpoints Monitor and tune redo logs Oracle Processes and Files Process Oracle file I/O Data files Log Archive Control CKPT Read/Write Read/Write DBWn Write LGWR Write Read/Write ARCn Read Write Read/Write SERVER Read/write Read Write Read/Write Oracle Processes and Files Whereas most server processes only read from disk, sort direct write server processes write to disk. The CKPT process only accesses the data file headers; the DBWn process writes out the actual table data. The server process reads the redo logs, writes to the archive logs, and read/writes to the control file under certain backup and recovery operations. For example, when performing manual archiving the user process that issued the statement performs the archiving process. Performance Guidelines Basic performance rules are as follows: Keep disk I/O to a minimum. Spread your disk load across disk devices and controllers. Use temporary tablespaces where appropriate. Performance Guidelines For very heavy OLTP applications, there are concurrency problems when using dictionary managed tablespaces because the dictionary must be accessed for space management operations during extent allocation. With locally managed tablespaces, there is no dictionary intervention, and therefore fewer concurrency problems. When users are created, a temporary tablespace is designated for any disk sorts and the creation of temporary tables. These areas should be separate from other database objects. If users do not have a temporary tablespace, then the default temporary tablespace is used. Tables and indexes should be split into separate tablespaces, because indexes and tables are often inserted into and read .