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Oracle9i physical memory management

Print View , by: iSee ,Total views: 16 ,Word Count: 760 ,Date: Tue, 25 Aug 2009 Time: 9:59 PM

In previous versions of Oracle9i, you can only start when the control of oracle database using Unix memory. Oracle provides some INIT.ORA parameters to detect the system global area (system global area, SGA) the size of the RAM. Once started the database, you will not be able to change the SGA size and configuration.

Oracle to a 24 / 7 database into the target memory area proposed to adjust the size of UNIX without having to stop and restart the database requirements. More importantly, Oracle9i dynamic SGA feature allows you to monitor the use of physical memory within the SGA and in accordance with the needs of the existing Oracle database, adjust the SGA memory areas.

Oracle9i also added a new memory management technology, enabling you to for all of the program global area (program global area, PGA) pre-allocated memory, and allows Oracle in accordance with the different needs of various types of connections to allocate memory for each connection. This is a traditional Oracle database, a very radical changes, but also makes SORT_AREA_SIZE and other PGA parameters are discarded.

Not only to the allocation of SGA, Oracle9i DBA must also be responsible for the UNIX Oracle server to allocate all the memory of the responsibility, but also as a UNIX management need to set aside 20% of memory.

In the previous version of Oracle9i also has several INIT.ORA parameter file is not uncommon, because it can easily adjust the database and re-configure the SGA to change the operating mode. For example, for online transaction processing (online transaction processing, OLTP) and the distribution of SGA and the Oracle data warehouse processing mode are very different.

Oracle recommended for OLTP databases and decision support systems (decision support system, DSS) applications - such as the Oracle data warehouse - to use a different memory configuration. OLTP system should be most UNIX memory allocated to the SGA, while the data warehouse and DSS applications that are more sensitive to the memory should be allocated the majority of the memory connected to the PGA.

Of course, if a database will operate in two ways, you can run a script to dynamically change the memory allocation. For example, if a database in OLTP mode during the day, while at night in order to DSS mode, then you can run a script from the SGA to take some memory out of the re-assigned to the PGA region.

alter system set sga_memory_max = 3g;

alter system set pga_aggregate_target = 3g;

In the Oracle9i in, Oracle provides the increase or decrease the size of SGA memory capacity of the following sections:

Data buffer size - alter system set db_cache_size = 300m;

Shared pool size - alter system set shared_pool_size = 200m;

Total PGA RAM memory size - alter system set pga_aggregate_target = 2000m;

In the UNIX on, Oracle by modifying the UNIX memory area of the physical address space to achieve the dynamic memory allocation purposes. You are on UNIX using malloc () and free () command can do.

The new dynamic SGA features that make Oracle SGA can start with a smaller capacity, and gradually increase as needed. In order to facilitate this process also provides a new SGA_MAX_SIZE parameters.

(Editor: Ming Ming mingming_ky@126.com TEL: (010) 68476606)

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