Introduction to the Oracle Server. This chapter provides an overview of the Oracle server. The topics include: An Oracle database is a collection of data treated as a unit. The purpose of a database is to store and retrieve related information.

Database Structure and Space Management Overview. An Oracle database is a collection of data treated as a unit. The purpose of a database is to store and retrieve.

Read Data Guard Physical Standby Database Best Practices – Part I. In this second part we will setup the standby database and enable Fast Start Fail Over.

• Rolling Forward a Physical Standby Database Using the RECOVER Command. A standby database is a transactionally-consistent copy of the production database.
• GoldenGate Creating a Physical Standby Database Using RMAN GoldenGate Tips by Donald BurlesonFebruary 17, 2016.
• 15 Maintaining and Troubleshooting the Management Repository. This chapter describes maintenance and troubleshooting techniques for maintaining a well-performing.

A database server is the key to solving the problems of information management. In general, a server reliably manages a large amount of data in a multiuser environment so that many users can concurrently access the same data. All this is accomplished while delivering high performance. A database server also prevents unauthorized access and provides efficient solutions for failure recovery.

The database has logical structures and physical structures. Because the physical and logical structures are separate, the physical storage of data can be managed without affecting the access to logical storage structures. Logical Database Structures. The logical structures of an Oracle database include schema objects, data blocks, extents, segments, and tablespaces. Schemas and Schema Objects. A schema is a collection of database objects. A schema is owned by a database user and has the same name as that user.

Schema objects are the logical structures that directly refer to the database's data. Schema objects include structures like tables, views, and indexes. Objects in the same schema can be in different tablespaces, and a tablespace can hold objects from different schemas.)Some of the most common schema objects are defined in the following section. See Also: Chapter 1. Database tables hold all user- accessible data. Each table has columns and rows. Oracle stores each row of a database table containing data for less than 2.

A table that has an employee database, for example, can have a column called employee number, and each row in that column is an employee's number. Views. Views are customized presentations of data in one or more tables or other views. A view can also be considered a stored query.

Views do not actually contain data. Rather, they derive their data from the tables on which they are based, referred to as the base tables of the views. Like tables, views can be queried, updated, inserted into, and deleted from, with some restrictions. All operations performed on a view actually affect the base tables of the view.

Views provide an additional level of table security by restricting access to a predetermined set of rows and columns of a table. They also hide data complexity and store complex queries. Indexes. Indexes are optional structures associated with tables. Indexes can be created to increase the performance of data retrieval. Just as the index in this manual helps you quickly locate specific information, an Oracle index provides an access path to table data. When processing a request, Oracle can use some or all of the available indexes to locate the requested rows efficiently. Indexes are useful when applications frequently query a table for a range of rows (for example, all employees with a salary greater than 1.

Indexes are created on one or more columns of a table. After it is created, an index is automatically maintained and used by Oracle.

Changes to table data (such as adding new rows, updating rows, or deleting rows) are automatically incorporated into all relevant indexes with complete transparency to the users. You can partition indexes. Clusters. Clusters are groups of one or more tables physically stored together because they share common columns and are often used together. Because related rows are physically stored together, disk access time improves.

Like indexes, clusters do not affect application design. Whether or not a table is part of a cluster is transparent to users and to applications. Data stored in a clustered table is accessed by SQL in the same way as data stored in a nonclustered table.

Data Blocks, Extents, and Segments. The logical storage structures, including data blocks, extents, and segments, enable Oracle to have fine- grained control of disk space use. Oracle Data Blocks. At the finest level of granularity, Oracle database data is stored in data blocks.

One data block corresponds to a specific number of bytes of physical database space on disk. The standard block size is specified by the initialization parameter DB. In addition, you can specify of up to five other block sizes. A database uses and allocates free database space in Oracle data blocks. See Also. An extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information. How To Install Php 5 On Centos 6. Segments. Above extents, the level of logical database storage is a segment.

A segment is a set of extents allocated for a certain logical structure. The following table describes the different types of segments.

Segment. Description. Data segment. Each nonclustered table has a data segment. All table data is stored in the extents of the data segment. For a partitioned table, each partition has a data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster's data segment. Cp Cheats Free Membership Hack.

Index segment. Each index has an index segment that stores all of its data. For a partitioned index, each partition has an index segment. Temporary segment. Temporary segments are created by Oracle when a SQL statement needs a temporary work area to complete execution.

When the statement finishes execution, the extents in the temporary segment are returned to the system for future use. Rollback segment. If you are operating in automatic undo management mode, then the database server manages undo space using tablespaces. Oracle Corporation recommends that you use . However, if you are operating in manual undo management mode, then one or more rollback segments for a database are created by the database administrator to temporarily store undo information.

The information in a rollback segment is used during database recovery: To generate read- consistent database information. Oracle dynamically allocates space when the existing extents of a segment become full. In other words, when the extents of a segment are full, Oracle allocates another extent for that segment. Because extents are allocated as needed, the extents of a segment may or may not be contiguous on disk.

See Also. For example, tablespaces commonly group together all application objects to simplify some administrative operations. Databases, Tablespaces, and Datafiles.

The relationship between databases, tablespaces, and datafiles (datafiles are described in the next section) is illustrated in Figure 1- 1. Figure 1- 1 Databases, Tablespaces, and Datafiles.

Text description of the illustration cncpt. This figure illustrates the following: Each database is logically divided into one or more tablespaces. One or more datafiles are explicitly created for each tablespace to physically store the data of all logical structures in a tablespace. The combined size of the datafiles in a tablespace is the total storage capacity of the tablespace.

A tablespace is generally online, so that users can access the information in the tablespace. However, sometimes a tablespace is taken offline to make a portion of the database unavailable while allowing normal access to the remainder of the database. This makes many administrative tasks easier to perform. Physical Database Structures. The following sections explain the physical database structures of an Oracle database, including datafiles, redo log files, and control files. Datafiles. Every Oracle database has one or more physical datafiles. The datafiles contain all the database data.

The data of logical database structures, such as tables and indexes, is physically stored in the datafiles allocated for a database. The characteristics of datafiles are: A datafile can be associated with only one database. Datafiles can have certain characteristics set to let them automatically extend when the database runs out of space. One or more datafiles form a logical unit of database storage called a tablespace, as discussed earlier in this chapter.