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The LARGE_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the large pool component of the SGA. The large pool is an optional component of the SGA. You must specifically set the LARGE_POOL_SIZE parameter if you want to create a large pool. Configuring the large pool is discussed in Oracle Database Performance Tuning Guide.[@more@]

The JAVA_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the java pool component of the SGA. Oracle Database selects an appropriate default value. Configuration of the java pool is discussed in Oracle Database Java Developer's Guide.[@more@]

The SHARED_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the shared pool component of the SGA. Oracle Database selects an appropriate default value.In releases before Oracle Database 10g Release 1, the amount of shared pool memory that was allocated was equal to the value of the SHARED_POOL_SIZE initialization parameter plus the amount of internal SGA overhead computed during instance startup. The internal SGA overhead refers to memory that

The sizes and numbers of nonstandard block size buffers are specified by the following initialization parameters:■ DB_2K_CACHE_SIZE ■ DB_4K_CACHE_SIZE ■ DB_8K_CACHE_SIZE ■ DB_16K_CACHE_SIZE ■ DB_32K_CACHE_SIZE Each parameter specifies the size of the buffer cache for the corresponding block size. For example:DB_BLOCK_SIZE=4096DB_CACHE_SIZE=12MDB_2K_CACHE_SIZE=8MDB_8K_CACHE_SIZE=4MIn this example, the parameters specify that the standard block size of the database is 4K. The size of the cach

The buffer cache initialization parameters determine the size of the buffer cache component of the SGA. You use them to specify the sizes of caches for the various block sizes used by the database. These initialization parameters are all dynamic.If you intend to use multiple block sizes in your database, you must have the DB_CACHE_SIZE and at least one DB_nK_CACHE_SIZE parameter set. Oracle Database assigns an appropriate default value to the DB_CACHE_SIZE parameter, but the DB_nK_CACHE_SIZE par

The DB_CACHE_SIZE initialization parameter has replaced the DB_BLOCK_BUFFERS initialization parameter, which was used in earlier releases. The DB_CACHE_SIZE parameter specifies the size in bytes of the cache of standard block size buffers. Thus, to specify a value for DB_CACHE_SIZE, you would determine the number of buffers that you need and multiple that value times the block size specified in DB_BLOCK_SIZE.For backward compatibility, the DB_BLOCK_BUFFERS parameter still functions, but it remai

If you decide not to use automatic shared memory management by not setting the SGA_TARGET parameter, you must manually configure each component of the SGA. This section provides guidelines on setting the parameters that control the size of each SGA components.[@more@]

Parameters for manually sized components can be dynamically altered as well. However, rather than setting a minimum size, the value of the parameter specifies the precise size of the corresponding component. When you increase the size of a manually sized component, extra memory is taken away from one or more automatically sized components. When you decrease the size of a manually sized component, the memory that is released is given to the automatically sized components.For example, consider thi

When SGA_TARGET is not set, the automatic shared memory management feature is not enabled. Therefore the rules governing resize for all component parameters are the same as in earlier releases. However, when automatic shared memory management is enabled, the manually specified sizes of automatically sized components serve as a lower bound for the size of the components. You can modify this limit dynamically by changing the values of the corresponding parameters.If the specified lower limit for t

When SGA_TARGET is not set,the automatic shared memory management feature is not enabled. Therefore the rulesgoverning resize for all component parameters are the same as in earlier releases.However, when automatic shared memory management is enabled, the manuallyspecified sizes of automatically sized components serve as a lower bound for the sizeof the components. You can modify this limit dynamically by changing the values ofthe corresponding parameters.If the specified lower limit for the siz

The SGA_TARGET parameter can be increased upto the value specified for the SGA_MAX_SIZE parameter, and it can also be reduced. Ifyou reduce the value of SGA_TARGET, the system identifies one or more automaticallytuned components for which to release memory. You can reduce SGA_TARGET untilone or more automatically tuned components reach their minimum size. OracleDatabase determines the minimum allowable value for SGA_TARGET taking intoaccount several factors, including values set for the automati

You can modify the value of SGA_TARGET andthe parameters controlling individual components dynamically using the ALTERSYSTEM statement, as described in "Using ALTER SYSTEM to Change InitializationParameter Values" on page2-38.[@more@]

When the automatic shared memory management feature is enabled, the internal tuningalgorithm tries to determine an optimal size forthe shared pool based on the workload. It usually converges on this value byincreasing in small increments over time. However, the internal tuning algorithmtypically does not attempt to shrink the shared pool, because the presence of opencursors, pinned PL/SQL packages, and other SQL execution state in the shared poolmake it impossible to find granules that can be fr

You can exercise some control over the size of the automatically sized SGA components byspecifying minimum values for the parameters corresponding to these components. Doing socan be useful if you know that an application cannot function properly without a minimumamount of memory in specific components. You specify the minimum amount of SGA spacefor a component by setting a value for its corresponding initialization parameter. Hereis an example configuration:■ SGA_TARGET = 256M■ SHARED_POOL_SI

摘自orafaqRestoring involves copying backup files from secondary storage (backup media) to disk. This can be done to replace damaged files or to copy/move a database to a new location.Recovery is the process of applying redo logs to the database to roll it forward. One can roll-forward until a specific point-in-time (before the disaster occurred), or roll-forward until the last transaction recorded in the log files.SQL> connect SYS as SYSDBASQL> RECOVER DATABASE UNTIL TIME '2001-03-06:16:0

摘自orafaqA hot (or on-line) backup is a backup performed while the database is open and available for use (read and write activity). Except for Oracle exports, one can only do on-line backups when the database is ARCHIVELOG mode.A cold (or off-line) backup is a backup performed while the database is off-line and unavailable to its users. Cold backups can be taken regardless if the database is in ARCHIVELOG or NOARCHIVELOG mode. It is easier to restore from off-line backups as no recovery (from

V$SGA V$SGA displays summary information about the system global area (SGA). Column Datatype Description NAME VARCHAR2(20) SGA component group VALUE NUMBER Memory size (in bytes) V$SGA_DYNAMIC_FREE_MEMORY V$SGA_DYNAMIC_FREE_MEMORY displays information about the amount of SGA memory available for future dynamic SGA resize operations. Column Datatype Description CURRENT_

To enable automatic shared memory management:1. If you are migrating from a manual management scheme, execute the followingquery on the instance running in manual mode to get a value for SGA_TARGET:SELECT ( (SELECT SUM(value) FROM V$SGA) - (SELECT CURRENT_SIZE FROM V$SGA_DYNAMIC_FREE_MEMORY) ) "SGA_TARGET"FROM DUAL;2. Set the value of SGA_TARGET, either by editing the text initialization parameterfile and restarting the database, or by issuing the following statement:ALTER SYSTEM

You enable the automatic shared memory management feature by setting the SGA_TARGET parameter to a non-zero value. This parameter in effect replaces the parameters that control the memory allocated for a specific set of individual components, which are now automatically and dynamically resized (tuned) as needed.Note: The STATISTICS_LEVEL initialization parameter must be set to TYPICAL (the default) or ALL for automatic shared memory management to function.The SGA_TARGET initialization parameter

The SGA_MAX_SIZE initialization parameter specifies the maximum size of the System Global Area for the lifetime of the instance. You can dynamically alter the initialization parameters affecting the size of the buffer caches, shared pool, large pool, Java pool, and streams pool but only to the extent that the sum of these sizes and the sizes of the other components of the SGA (fixed SGA, variable SGA, and redo log buffers) does not exceed the value specified by SGA_MAX_SIZE.If you do not specify