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The SGA comprises a number of memory components, which are pools of memory used to satisfy a particular class of memory allocation requests. Examples of memory components include the shared pool (used to allocate memory for SQL and PL/SQL execution), the java pool (used for java objects and other java execution memory), and the buffer cache (used for caching disk blocks). All SGA components allocate and deallocate space in units of granules. Oracle Database tracks SGA memory use in internal numb

This section discusses the initialization parameters that affect the amount of memory allocated to the System Global Area (SGA). Except for the SGA_MAX_SIZE initialization parameter, they are dynamic parameters whose values can be changed by the ALTER SYSTEM statement. The size of the SGA is dynamic, and can grow or shrink by dynamically altering these parameters.管理SGA1. SGA_MAX_SIZE 是静态参数2. 其他都是动态参数, 可以使用ALTER SYSTEM 语句动态修改的参数.[@more@]

Tablespaces of nonstandard block sizes can be created using the CREATE TABLESPACE statement and specifying the BLOCKSIZE clause. These nonstandard block sizes can have any of the following power-of-two values: 2K, 4K, 8K, 16K or 32K. Platform-specific restrictions regarding the maximum block size apply, so some of these sizes may not be allowed on some platforms.To use nonstandard block sizes, you must configure subcaches within the buffer cache area of the SGA memory for all of the nonstandard

The most commonly used block size should be picked as the standard block size. In many cases, this is the only block size that you need to specify. Typically, DB_BLOCK_SIZE is set to either 4K or 8K. If you do not set a value for this parameter, the default data block size is operating system specific, which is generally adequate. You cannot change the block size after database creation except by re-creating the database. If the database block size is different from the operating system block si

The DB_BLOCK_SIZE initialization parameter specifies the standard block size for thedatabase. This block size is used for the SYSTEM tablespace and by default in other tablespaces. Oracle Database can support up to four additional nonstandard block sizes.指定数据块大小1. DB_BLOCK_SIZE指定标准块大小2. 指定了system表空间和其他默认表空间的块大小[@more@]

The CONTROL_FILES initialization parameter specifies one or more control filenames for the database. When you execute the CREATE DATABASE statement, the control files listed in the CONTROL_FILES parameter are created.If you do not include CONTROL_FILES in the initialization parameter file, then Oracle Database creates a control file using a default operating system dependent filename or, if you have enabled Oracle-managed files, creates Oracle-managed control files.If you want the database to cr

A flash recovery area is a location in which Oracle Database can store and manage files related to backup and recovery. It is distinct from the database area, which is a location for the Oracle-managed current database files (datafiles, control files, and online redo logs).You specify a flash recovery area with the following initialization parameters:■ DB_RECOVERY_FILE_DEST: Location of the flash recovery area. This can be a directory, file system, or Automatic Storage Management (ASM) disk gro

DB_DOMAIN is a text string that specifies the network domain where the database is created. This is typically the name of the organization that owns the database. If the database you are about to create will ever be part of a distributed database system, give special attention to this initialization parameter before database creation.初始化参数 : DB_DOMAIN1. 该参数指定创建的数据库的网络域名2. 如果该数据库有可能是一个分布式数据库系统的一部分 , 对于该参数需要给与特定的关注[@more@]

DB_NAME must be set to a text string of no more than eight characters. During database creation, the name provided for DB_NAME is recorded in the datafiles, redo log files, and control file of the database. If during database instance startup the value of the DB_NAME parameter (in the parameter file) and the database name in the control file are not the same, the database does not start.初始化参数 : DB_NAME1. 需要是少于8个字符的文本串2. 该参数记录在数据文件, 重做日志文件 和控制文件中3.

The global database name consists of the user-specified local database name and the location of the database within a network structure. The DB_NAME initialization parameter determines the local name component of the database name, and the DB_DOMAIN parameter indicates the domain (logical location) within a network structure. The combination of the settings for these two parameters must form a database name that is unique within a network.For example, to create a database with a global database

When an Oracle instance starts, it reads initialization parameters from an initialization parameter file. This file can be either a read-only text file, or a read/write binary file. The binary file is called a server parameter file, and it always resides on the server. A server parameter file enables you to change initialization parameters with ALTER SYSTEM commands and to persist the changes across a shutdown and startup. It also provides a basis for self-tuning by the Oracle Database server. F

FORCE LOGGING mode results in some performance degradation. If the primary reason for specifying FORCE LOGGING is to ensure complete media recovery, and there is no standby database active, then consider the following:■ How many media failures are likely to happen?■ How serious is the damage if unlogged direct writes cannot be recovered?■ Is the performance degradation caused by forced logging tolerable?If the database is running in NOARCHIVELOG mode, then generally there is no benefit to pla

To put the database into FORCE LOGGING mode, use the FORCE LOGGING clause in the CREATE DATABASE statement. If you do not specify this clause, the database is not placed into FORCE LOGGING mode. Use the ALTER DATABASE statement to place the database into FORCE LOGGING mode after database creation. This statement can take a considerable time for completion, because it waits for all unlogged direct writes to complete.You can cancel FORCE LOGGING mode using the following SQL statement:ALTER DATABAS

Some data definition language statements (such as CREATE TABLE) allow the NOLOGGING clause, which causes some database operations not to generate redo records in the database redo log. The NOLOGGING setting can speed up operations that can be easily recovered outside of the database recovery mechanisms, but it can negatively affect media recovery and standby databases.Oracle Database lets you force the writing of redo records even when NOLOGGING has been specified in DDL statements. The database

Two time zone files are included in the Oracle home directory. The default time zone file is $ORACLE_HOME/oracore/zoneinfo/timezonelrg.dat. A smaller time zone file can be found in $ORACLE_HOME/oracore/zoneinfo/timezone.dat.If you are already using the smaller time zone file and you want to continue to use it in an Oracle Database 10g environment or if you want to use the smaller time zone file instead of the default time zone file, then complete the following tasks:1. Shut down the database.2.

Set the database time zone when the database is created by using the SET TIME_ZONE clause of the CREATE DATABASE statement. If you do not set the database time zone, then it defaults to the time zone of the server's operating system.You can change the database time zone for a session by using the SET TIME_ZONE clause of the ALTER SESSION stateme设置数据库时区1. 可通过SET TIME_ZONE 语句设置数据库的时区 , 默认与操作系统相同2. 可为不同的会话指定不同的时区[@more@]

The SYSTEM and SYSAUX tablespaces are always created with the default tablespacetype. However, you can explicitly override the default tablespace type for the UNDOand DEFAULT TEMPORARY tablespace during the CREATE DATABASE operation.For example, you can create a bigfile UNDO tablespace in a database with the defaulttablespace type of smallfile as follows:CREATE DATABASE rbdb1... BIGFILE UNDO TABLESPACE undotbs DATAFILE '/u01/oracle/oradata/mynewdb/undotbs01.dbf' SIZE 200M REUSE

The SET DEFAULT...TABLESPACE clause of the CREATE DATABASE statement todetermines the default type of tablespace for this database in subsequent CREATETABLESPACE statements. Specify either SET DEFAULT BIGFILE TABLESPACE orSET DEFAULT SMALLFILE TABLESPACE. If you omit this clause, the default is asmallfile tablespace, which is the traditional type of Oracle Database tablespace. Asmallfile tablespace can contain up to 1022 files with up to 4M blocks each.The use of bigfile tablespaces further enha

Oracle Database simplifies management of tablespaces and enables support forultra-large databases by letting you create bigfile tablespaces. Bigfile tablespaces cancontain only one file, but that file can have up to 4G blocks. The maximum number ofdatafiles in an Oracle Database is limited (usually to 64K files). Therefore, bigfiletablespaces can significantly enhance the storage capacity of an Oracle Database.数据库创建过程中支持大文件表空间操作1. 大文件表空间只能有1个数据文件 , 该文件最大可

You can minimize the number of clauses and parameters that you specify in your CREATE DATABASE statement by using the Oracle-managed files feature. You do this either by specifying a directory in which your files are created and managed by Oracle Database, or by using Automatic Storage Management. When you use Automatic Storage Management, you specify a disk group in which the database creates and manages your files, including file redundancy and striping. By including any of the initialization