This section provides background information on the automatic memory management feature of Oracle Database, and includes instructions for enabling this feature. The following topics are covered: Metamovie add metadata to your videos 2 4 3.
- Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Examples
- Memorytamer 1 5 0 – Automatic Memory Freeing Approaches List
- Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Worksheet
- Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Chart
- The Garbage Collection Handbook is the most up-to-date, detailed, and exhaustive collation and description of the current state of the art of Garbage Collection and Automatic Memory Management available today. It is an imperative reference book for anyone working in the field, and I would consider it the textbook of reference covering GC 101 thru GC 530 course levels, if such courses were.
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About Automatic Memory Management
The simplest way to manage instance memory is to allow the Oracle Database instance to automatically manage and tune it for you. To do so (on most platforms), you set only a target memory size initialization parameter (
MEMORY_TARGET
) and optionally a maximum memory size initialization parameter (MEMORY_MAX_TARGET
). The instance then tunes to the target memory size, redistributing memory as needed between the system global area (SGA) and the instance program global area (instance PGA). Because the target memory initialization parameter is dynamic, you can change the target memory size at any time without restarting the database. The maximum memory size serves as an upper limit so that you cannot accidentally set the target memory size too high, and so that enough memory is set aside for the Oracle Database instance in case you do want to increase total instance memory in the future. Because certain SGA components either cannot easily shrink or must remain at a minimum size, the instance also prevents you from setting the target memory size too low.If you create your database with Database Configuration Assistant (DBCA) and choose the basic installation option, automatic memory management is enabled. If you choose advanced installation, Database Configuration Assistant (DBCA) enables you to select automatic memory management.
Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Examples
Ual memory management efficiently, without compromising safety. Previous approaches to safe manual memory manage-ment use programming models based on regions 20, 40, unique pointers 22, 38, borrowing of references 11, 12, 42, and ownership types 10, 12, 13. For example, Rust 5 is a recent programming language that incorporates several.
Note:
You cannot enable automatic memory management if the LOCK_SGA
initialization parameter is TRUE
. See Oracle Database Reference for information about this parameter.See Also:
Enabling Automatic Memory Management
If you did not enable automatic memory management upon database creation (either by selecting the proper options in DBCA or by setting the appropriate initialization parameters for the
CREATE DATABASE
SQL statement), you can enable it at a later time. Enabling automatic memory management involves a shutdown and restart of the database.To enable automatic memory management
- Start SQL*Plus and connect to the database as
SYSDBA
.See 'About Database Administrator Security and Privileges' and 'Database Administrator Authentication' for instructions. - Calculate the minimum value for
MEMORY_TARGET
as follows:- Determine the current sizes of
SGA_TARGET
andPGA_AGGREGATE_TARGET
by entering the following SQL*Plus command:SQL*Plus displays the values of all initialization parameters with the stringTARGET
in the parameter name. - Run the following query to determine the maximum instance PGA allocated since the database was started:
- Compute the maximum value between the query result from step 2b and
PGA_AGGREGATE_TARGET
. AddSGA_TARGET
to this value.
For example, ifSGA_TARGET
is 272M andPGA_AGGREGATE_TARGET
is 90M as shown above, and if the maximum PGA allocated is determined to be 120M, thenMEMORY_TARGET
should be at least 392M (272M + 120M). - Choose the value for
MEMORY_TARGET
that you want to use.This can be the minimum value that you computed in step 2, or you can choose to use a larger value if you have enough physical memory available. - For the
MEMORY_MAX_TARGET
initialization parameter, decide on a maximum amount of memory that you would want to allocate to the database for the foreseeable future. That is, determine the maximum value for the sum of the SGA and instance PGA sizes. This number can be larger than or the same as theMEMORY_TARGET
value that you chose in the previous step. - Do one of the following:
- If you started your Oracle Database instance with a server parameter file, which is the default if you created the database with the Database Configuration Assistant (DBCA), enter the following command:where n is the value that you computed in Step 4.The
SCOPE
=
SPFILE
clause sets the value only in the server parameter file, and not for the running instance. You must include thisSCOPE
clause becauseMEMORY_MAX_TARGET
Recoverit video repair 1 1 0 4. is not a dynamic initialization parameter. - If you started your instance with a text initialization parameter file, manually edit the file so that it contains the following statements:where n is the value that you determined in Step 4, and m is the value that you determined in step 3.
Note:In a text initialization parameter file, if you omit the line forMEMORY_MAX_TARGET
and include a value forMEMORY_TARGET
, the database automatically setsMEMORY_MAX_TARGET
to the value ofMEMORY_TARGET
. If you omit the line forMEMORY_TARGET
and include a value forMEMORY_MAX_TARGET
, theMEMORY_TARGET
parameter defaults to zero. After startup, you can then dynamically changeMEMORY_TARGET
to a nonzero value, provided that it does not exceed the value ofMEMORY_MAX_TARGET
. - Shut down and restart the database.Etrecheck pro 5 1 – for troubleshooting your macbook pro. See Chapter 3, 'Starting Up and Shutting Down' for instructions.
- If you started your Oracle Database instance with a server parameter file, enter the following commands:where n is the value that you determined in step 3.
Note:
The preceding steps instruct you to set SGA_TARGET
and Memorytamer 1 5 0 – Automatic Memory Freeing Approaches List
PGA_AGGREGATE_TARGET
Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Worksheet
to zero so that the sizes of the SGA and instance PGA are tuned up and down as required, without restrictions. You can omit the statements that set these parameter values to zero and leave either or both of the values as positive numbers. In this case, the values act as minimum values for the sizes of the SGA or instance PGA.See Also:
- Oracle Database SQL Language Reference for information on the
ALTER
SYSTEM
SQL statement
Monitoring and Tuning Automatic Memory Management
Memorytamer 1 5 0 – Automatic Memory Freeing Approaches Chart
The dynamic performance view
V$MEMORY_DYNAMIC_COMPONENTS
shows the current sizes of all dynamically tuned memory components, including the total sizes of the SGA and instance PGA.The view
V$MEMORY_TARGET_ADVICE
provides tuning advice for the MEMORY_TARGET
initialization parameter.The row with the
MEMORY_SIZE_FACTOR
of 1 shows the current size of memory, as set by the MEMORY_TARGET
initialization parameter, and the amount of DB time required to complete the current workload. In previous and subsequent rows, the results show a number of alternative MEMORY_TARGET
sizes. For each alternative size, the database shows the size factor (the multiple of the current size), and the estimated DB time to complete the current workload if the MEMORY_TARGET
parameter were changed to the alternative size. Notice that for a total memory size smaller than the current MEMORY_TARGET
size, estimated DB time increases. Notice also that in this example, there is nothing to be gained by increasing total memory size beyond 450MB. However, this situation might change if a complete workload has not yet been run.Enterprise Manager provides an easy-to-use graphical memory advisor to help you select an optimal size for
MEMORY_TARGET
. See Oracle Database 2 Day DBA for details.See Also:
- Oracle Database Reference for more information about these dynamic performance views
- Oracle Database Performance Tuning Guide for a definition of DB time.