![]() ![]() Oracle ASM manages the disk space, distributing the I/O load across all available resources to optimize performance while removing the need for manual I/O tuning. To use Oracle ASM, you allocate partitioned disks for Oracle Database with preferences for striping and mirroring. Rebalances data automatically after storage configuration changes Simplifies storage-related tasks such as creating and laying out databases and managing disk spaceĭistributes data across physical disks to eliminate hot spots and to provide uniform performance across the disks Oracle ASM provides several advantages over conventional file systems and storage managers, including the following: Oracle ASM is a volume manager and provides a file system designed exclusively for use by the database. Oracle ASM is a high-performance, ease-of-management storage solution for Oracle Database files. For example, a database could store the control files and online redo log files in a traditional file system, some user data files on raw partitions, the remaining data files in Oracle ASM, and archived the redo log files to a cluster file system. In an operating system file system, however, if a computer sharing files through NFS or other means fails, then the file system is unavailable.Ī database employs a combination of the preceding storage mechanisms. With a cluster file system, the failure of a computer in the cluster does not make the file system unavailable. In an Oracle RAC environment, a cluster file system makes shared storage appears as a file system shared by many computers in a clustered environment. Historically, raw devices were the only means of implementing direct I/O.Ī cluster file system is software that enables multiple computers to share file storage while maintaining consistent space allocation and file content. Many file systems now support direct I/O for databases and other applications that manage their own caches. In direct I/O, applications write to and read from the storage device directly, bypassing the operating system buffer cache. The primary benefit of raw devices is the ability to perform direct I/O and to write larger buffers. Raw devices are disk partitions or logical volumes not formatted with a file system. The LVM enables pieces of multiple physical disks to be combined into a single contiguous address space that appears as one disk to higher layers of software. The database can create, read, write, resize, and delete files.Ī file system is commonly built on top of a logical volume constructed by a software package called a logical volume manager (LVM). Each file has a name and is made to appear as a contiguous address space to applications such as Oracle Database. All operating systems have file managers that allocate and deallocate disk space into files within a file system.Ī file system enables disk space to be allocated to many files. ![]() Most Oracle databases store files in a file system, which is a data structure built inside a contiguous disk address space. "Oracle Automatic Storage Management (Oracle ASM)" describes Oracle ASM. Oracle ASM includes a file system designed exclusively for use by Oracle Database. Oracle Automatic Storage Management (Oracle ASM) Several mechanisms are available for allocating and managing the storage of these files. Figure 11-1 shows the relationship between the instance and the files that it manages. The online redo log is a set of files containing records of changes made to data.Ī database instance is a set of memory structures that manage database files. The data is written to these files in an Oracle proprietary format that cannot be read by other programs.Ī control file is a root file that tracks the physical components of the database. A temp file is a data file that belongs to a temporary tablespace. This section discusses the database files generated when you issue a CREATE DATABASE statement:Ī data file is a physical file on disk that was created by Oracle Database and contains data structures such as tables and indexes. For example, renaming a database file does not rename the tables stored in it.Īn Oracle database is a set of files that store Oracle data in persistent disk storage. Because physical and logical structures are separate, you can manage physical storage of data without affecting access to logical structures. One characteristic of an RDBMS is the independence of logical data structures such as tables, views, and indexes from physical storage structures. Introduction to Physical Storage Structures ![]()
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