pga superstore

Oracle memory: memory architecture: oracle database allocates memory and background processes whenever the database instance is started, the following information is stored in the memory area: program code and connection session information, even if the session is not active." Information required during program execution, information about data sharing locks. Buffered data, data blocks, redo log records, and so on. You can check the figure above: A) The basic memory structure includes the follo

Instance and a database (data file, control file, and redo log file). The so-called Instance is the medium for user interaction with the database, you can operate a database by connecting to an instance. The instance is composed of a unified memory structure (SGA, PGA, UGA) and a batch of memory resident processes. The instance is identified by ORACLE_SID in the operating system and the INSTANCE_NAME parameter in Oracle. The values of the two instanc

managed and allocated, and 11g can automatically manage SGA, you can also automatically manage PGA and manage these two parts comprehensively to automatically adjust the size of all memory areas. The default value is 0 in 11g. Now let's list the syntax of these parameters. This is a static parameter that needs to be restarted to take effect. Alter systemset memory_max_target = 1000 m scope = spfile;Alter system set memory_target = 1000 m scope = spfi

In Oracle, the memory structure mainly includes two categories: SGA and PGA. SGA represents the system global zone, and PGA represents the program global zone. Oracle memory mainly stores execution processes In Oracle, the memory structure mainly includes two categories: SGA and PGA. SGA represents the system global zone, and

ORACLE Database Performance Optimization-) memory disk1. Memory Structure Optimization Overview 1.1 buffer zone Buffer zones that affect database performance include SGA that can be shared and pga that are private to server processes, sga also includes the Shared Pool, large pool, java pool, data buffer, stream pool, and redo log buffer.1.2 Automatic Memory Management Oracle generally uses automatic memory management to manage system memory. oracle au

bridging sensor signals that require extremely high-precision measurements, many electronic scaling vendors have used an extremely low noise gain level to zoom in on signals from bridging before digitization. The gain-level bandwidth is usually not a big problem when the weights on many electronic scales change slowly. However, the key is that the gain level can be very stable in both temperature and time changes. Most electronic scales only require regular calibration by the manufacturer or us

"Meet the Cursor sharing condition. It can be shared before it is out of age or flushed out of memory. If the same SQL statement is issued for the second time, Shared Cursor is Shared, which is called Soft Parse. Private Cursor corresponds to Shared Cursor. Private Cursor is resident in the PGA space of the Server Process. When we issue an SQL statement or manually create a Cursor, a Private Cursor object is created in the

process that corresponds to a user process Shared service process (multitreaded server process): A service processing corresponds to multiple user processes and takes turns serving the user process. The dedicated server mode means that each time the Oracle server is accessed, the listener of the system receives the access request and then creates a new process for the access to service. So, for each client access, will generate a new process for service, is a similar one-to-one mapping relation

required. Soft parsing also requires scanning the library to cache object handle chains to find reusable parse trees and execution plans, so there is inevitably contention for library cache latch. But compared to hard parsing, the first, soft-analytic library cache latch contention is much less, the library cache latch holding time will be relatively short.SummarizeIf soft parsing is widely used in OLTP-type systems when executing target SQL, the performance and scalability of the system will b

slowly come.Memory structure, the memory structure mainly includes the PGA and SGA,PGA is for the client Access Time service, the SGA is the database operation service, these after the machine power down disappeared.There are also the main 6 process PMON,SMON,DBWR,LGWR,CHPT,ARCN, which are only available when the database is started.The bottom is stored in the persistent media files, have archived logs, da

to mention the book appeared, there are many masters of the speeches. But we do not care about those, according to our own rhythm to write down characteristics, remember the wonderful. First insert the first picture of this series, figure one (absolutely from the official website), see how careful Toad for the picture use, if everyone has their own unique understanding of this figure, then you can skip this note directly, of course, it is also possible to know the new shame, and then Yong ....

Each time you modify these blocks in cachebuffer, you must first generate the corresponding changevector in PGA, and then the serverprocess from PGAcopy to SGAREDOLOG Each time you modify these blocks in the cache buffer, you must first generate the corresponding change vector in the PGA, and then copy the data from the server process to the SGA REDO LOG The redo log file is composed of redo records (als

statements. The data dictinary cache holds the most recently used database dictionary information. The data ditinary CacheIs also known as the row cache because it holds data as rows instead of buffers (which hold entire blocks of data ). Program global area:The program global area (PGA) is the area in the memory that contains the data and process information for one process, and this area is non-shared memory. The contents of the

AdvisorMemory: The physical zone loaded on the physical memory. One part is called SGA and the other part is called the original process. Key database files: Database Control Files, data files, and redoOther key datafiles: backup file, TRC file, spfile Shared Pool: parses SQL statements and stores SQL statements.Database Buffer: data block bufferJava pool: required by JVM. External stored procedure is called.Large pool: Backup RecoveryStream poll: Advanced Replication (available in Oracle 10)Pg

1. directpath reads description In versions earlier than Oracle 11g, if a full table scan is performed on a large table, the wait event is: DB file scattered read; in 11g, if a full table scan is performed on a large table, wait event is: direct path read; that is, in 11 GB, full table scan of large tables directly reads data blocks into the PGA region of the session. (For more information, see the following example ). In 11g, data blocks are directl

Bkjia.com exclusive Translation]Oracle has made great efforts in simplifying memory management over the past few years. Since Oracle 9i implements automatic PGA management through the PGA_AGGREGATE_TARGET parameter, Oracle 10g implements automatic SGA management through the SGA_TARGET parameter, oracle 11g is surprisingly capable of fully automatic management of all the memory blocks of the database. It makes dynamic management of SGA and

| | | | --------------------------------------------------------------------------------------------------------------- --predicate information (identified by Operation ID):---------------------------------------------------4-acce SS ("T3".) ID "=" T4 "." t3_id ") filter("T3".) ID "=" T4 "." t3_id ") 5-filter (" T3 "). N "=1100) From the result of the return execution plan, we can see:1. T3 as the driving table and T4 as the driving table, both cost (a-time) and buffers are almo

Term definitionsActive Session Pool resource group or sub-plan number of currently active sessions allowedADDM Automatic Database Diagnostic Monitor (automatic DB diagnostic monitoringProgramASM Automatic Storage Management (Automatic storage Management)ASM Automatic Summary Management (Automatic profile Management)ASMM Automatic Shared Memory Management (automatic management of sharing RAM)ASSM Automatic Segment Space Management (automatic segment space management)ATO Automatic Tuning Optimizer

reverse is true: only one instance of a database operates on it. However, Oracle's real application cluster (real application Clusters,rac) is an exception, This is an option provided by Oracle that allows operations on multiple computers in a clustered environment so that multiple instances can mount and open a database (on a shared set of physical disks) at the same time. As a result, we can access this database from several different computers at the same time. Oracle RAC supports highly ava

):---------------------------------------------------4-access (" T3 "." ID "=" T4 "." t3_id ") filter (" T3 "." ID "=" T4 "." t3_id ") 5-filter (" T3 ")." N "=1100)From the results of the returned execution plan we can see:1. The cost (a-time) and buffers of the T3 are the same as the driver table and the T4 as the driver table.2. With T3 as the driver table, T3 Access once, T4 is also visited once; With T4 as the driver table, T4 Access once, T3 is also visited once3. Sorting required if the