After completing this lesson, you should be able to do the following: Implement dynamic SGA allocation Dynamically adjust the buffer caches Dynamically adjust the shared pool | Dynamic Instance Resizing Objectives After completing this lesson, you should be able to do the following: Implement dynamic SGA allocation Dynamically adjust the buffer caches Dynamically adjust the shared pool Dynamic SGA Feature The dynamic SGA feature implements an infrastructure to allow the server to change its SGA configuration without shutting down the instance. SGA is limited by SGA_MAX_SIZE. A dynamic SGA can grow and shrink in response to a DBA command. Dynamic SGA The SGA has always been a static allocation of memory, which was shared across all threads of execution. The dynamic SGA infrastructure allows for the sizing of the buffer cache and shared pool without having to shut down the instance, modify the initialization parameter file, and restart the instance. In addition, the dynamic SGA infrastructure allows limits to be set at run time on how much physical memory is used for the SGA. The parameter that limits the memory is SGA_MAX_SIZE. This amount of memory is . | Dynamic Instance Resizing Objectives After completing this lesson, you should be able to do the following: Implement dynamic SGA allocation Dynamically adjust the buffer caches Dynamically adjust the shared pool Dynamic SGA Feature The dynamic SGA feature implements an infrastructure to allow the server to change its SGA configuration without shutting down the instance. SGA is limited by SGA_MAX_SIZE. A dynamic SGA can grow and shrink in response to a DBA command. Dynamic SGA The SGA has always been a static allocation of memory, which was shared across all threads of execution. The dynamic SGA infrastructure allows for the sizing of the buffer cache and shared pool without having to shut down the instance, modify the initialization parameter file, and restart the instance. In addition, the dynamic SGA infrastructure allows limits to be set at run time on how much physical memory is used for the SGA. The parameter that limits the memory is SGA_MAX_SIZE. This amount of memory is allocated at startup of the instance, regardless of whether the individual components utilize the entire amount of memory. You should configure instances to start with less than the maximum amount of memory the operating system makes available and allow the DBA to modify the SGA components as needed. Unit of Allocation in the Dynamic SGA In the dynamic SGA model, the unit of memory allocation is called a granule. SGA memory is tracked in granules by SGA components. A granule is a unit of contiguous virtual memory allocation. Use v$buffer_pool to monitor size of the buffer caches. Unit of Allocation in the Dynamic SGA The columns in v$buffer_pool are: id: Buffer pool identifying number name: Buffer pool name block_size: Block size for buffers in this component resize_state: Current state of the resize operation (values Static, Allocating, Activating, or Shrinking) current_size: Present size of the pool in megabytes buffers: Current instantaneous number of buffers target_size: New size, in .
