What is the SGA in Oracle?

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In the database management systems developed by the Oracle Corporation, the System Global Area (SGA) forms the part of the system memory (RAM) shared by all the processes belonging to a single Oracle database instance. The SGA contains all information necessary for the instance operation.

What is dynamic SGA? Dynamic SGA allows to change the size of the buffer cache, the large pool, the shared pool and the process private memory on the fly, that is without shutting down the instance.

what is SGA and PGA in Oracle?

Basic Memory Structures The SGA is a group of shared memory structures, known as SGA components, that contain data and control information for one Oracle Database instance. A PGA is a nonshared memory region that contains data and control information exclusively for use by an Oracle process.

What is a tablespace in Oracle? An Oracle database consists of one or more logical storage units called tablespaces, which collectively store all of the database’s data. Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that conform to the operating system in which Oracle is running.

what is Oracle PGA?

The Program Global Area (PGA) is a private memory region that contains the data and control information for a server process. Only a server process can access the PGA. Oracle Database reads and writes information in the PGA on behalf of the server process.

What is Sga_max_size?

SGA_MAX_SIZE. SGA_MAX_SIZE specifies the maximum size of the SGA for the lifetime of the instance. On 64-bit platforms and non-Windows 32-bit platforms, when either MEMORY_TARGET or MEMORY_MAX_TARGET is specified, the default value of SGA_MAX_SIZE is set to the larger of the two parameters.

what is Oracle SGA size?

The SGA (System Global Area) is an area of memory (RAM) allocated when an Oracle Instance starts up. The SGA’s size and function are controlled by initialization (INIT. ORA or SPFILE) parameters.

What is Sga_target & Sga_max_size?

SGA_MAX_SIZE and SGA_TARGET both are the parameter are used to change the SGA SIZE. it specifies the total amount of SGA memory available to an instance. This feature is called Automatic Shared Memory Management. With ASMM, the parameters java_pool_size, shared_pool_size, large_pool_size and db_cache_size are affected.

What are the components of SGA in Oracle?

The SGA contains the following data structures:

What is Sga_target?

SGA_TARGET is a database initialization parameter (introduced in Oracle 10g) that can be used for automatic SGA memory sizing. Single parameter for total SGA size. Automatically sizes SGA components. Memory is transferred to where most needed. Uses workload information.

What is the difference between PGA and SGA in Oracle?

The basic difference between SGA and PGA is that PGA cannot be shared between multiple processes, in the sense, that it is used only for requirements of a particular process whereas the SGA is used for the whole instance and it is shared.

What is large pool in Oracle?

Oracle Large Pool is an optional memory component of the oracle database SGA. This area is used for providing large memory allocations in many situations that arise during the operations of an oracle database instance.

What is Pga_aggregate_target?

PGA_AGGREGATE_TARGET is a database initialization parameter and controls the total amount of execution memory that can be allocated by Oracle for the Process global area (PGA) PGA_AGGREGATE_TARGET = (TOTAL_MEM * 80%) * 50% The Total Memory here refers to the total memory available in the system.

What is Pga_aggregate_limit?

PGA_AGGREGATE_LIMIT specifies a limit on the aggregate PGA memory consumed by the instance. There is no difference in behavior between PGA_AGGREGATE_LIMIT being explicitly set or being set to the default. Actions Taken When PGA_AGGREGATE_LIMIT is Exceeded. Parallel queries will be treated as a unit.

What is redo buffer in Oracle?

The Redo Log Buffer A log buffer is a circular buffer in the SGA that holds information about changes made to the database. Redo entries contain the information necessary to reconstruct or redo changes made to the database by insert, update, delete, create, alter, or drop operations.

What is data buffer cache in Oracle?

The Oracle database buffer cache is also referred to as buffer cache. The buffer cache stores copies of data blocks in memory (the SGA). These copies are stored in what is called buffers by Oracle. When a dirty buffer is not used anymore, it is written to disk by the Database Writer background process.