ORACLE 11G ARCHITECTURE PDF
Oracle Database Concepts, 11g Release 2 (). E Copyright © .. Oracle Database Architecture. Application and Networking Architecture. Oracle Database Concepts, 11g Release 1 (). B . Overview of Application Architecture. Multitier Architecture: Service-Oriented Architecture. Oracle Database Administrator's Guide, 11g Release 2 (). E Copyright © , , Oracle and/or its affiliates. All rights reserved. Primary.
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To Download in PDF: 11g Architecture in PDF. Soon I will 11g Dynamic v$ Performance ViewsOctober 2, In "ORACLE DATABASE". Oracle Architecture Diagram and Notes - Free download as PDF File .pdf), Text File .txt) or read online for Oracle Database 11g SQL Tuning wildlifeprotection.info preferably some knowledge of Oracle an introduction to the architecture of Oracle . The following •The Oracle Server itself, which is were the database resides.
If a process cannot be granted the lock because it is incompatible with the mode requested and the lock is requested with wait, the OS puts the requesting process on a wait queue which is serviced in FIFO. Advantages Allows several concurrent processes to have varying degree of known resources. If a process cannot be granted lock then it puts the process in wait queue. There is ordered queue of waiters. Differences between Latches and Enqueues Latches - Low level of serialization.
Enqueue - Concurrency Latches - Process acquires latch for a short time and there is no ordered queue of waiters. Enqueue Obtained using OS Specific locking mechanism, there are waiters. These are small data structures, such as latches and pointers, which refer to other areas of the SGA. The size of the fixed area is static. It also contains general information about the state of the database and the instance which the background processes need to access.
When Oracle receives a request to retrieve data, it will first check the internal memory structures to see if the data is already in the buffer. Following are its Tasks Storage for data blocks that have been retrieved from data files. When Oracle SQL updates a table a process called Data Manipulation Language, or DML , redo images are created and stored in the redo log buffer Serves for assistance with database recovery tasks Records all changes made to database blocks Places changes recorded to redo entries for redo logs Oracle will eventually flush the redo log buffer to disk, only after a commit operation occurs.
The JAVA pool is used by many internal routines, such as import and export, and should be sized at approximately 60 megabytes if no other JAVA will be utilized in the user applications. Thus the SEP is always in the SGA since it tracks sort extents but the actual sort extents themselves are in several areas. In some cases, such as in the case of reorganizing large tables that involves a large-volume data load, the DBA may grant the restricted session privilege to a developer who is assisting in the database maintenance work.
In these situations, the DBA may want to consider a temporary grant of restricted session to the developer, followed by a revocation of the privilege afterward to prevent possible data integrity issues in later maintenance cycles. This method is generally preferable to a permanent grant of restricted session to someone outside the DBA organization.
Typically, the DBA will want to use the restrict option for logical database object maintenance such as reorganizing tablespaces, creating new indexes or fixing old ones, large-volume data loads, reorganizing or renaming objects, and other DBA maintenance activities.
There are two special cases for database startup left to consider, both of which are used for circumstances outside of normal database activity. One of those two situations is when the database has experienced a failure of some sort that requires the DBA to perform a complete database recovery of the database and the instance. In this case, the DBA may want the instance to initiate its complete recovery at the time the instance is started.
To accomplish the task, the DBA can issue the startup recover command from the Server Manager tool, and Oracle will start the instance and initiate the complete recovery at instance startup. In cases where archiving is used, Oracle may require certain archived redo logs to be present for this option to complete successfully.
In any event, the use of this option will be more carefully considered in the next unit, the treatment of OCP Exam 3 on database backup and recovery. The final option for database startup is used in unusual circumstances as well. Sometimes rarely there is a situation where the Oracle database cannot start the instance under normal circumstances or shut down properly due to some issue with memory management or disk resource management. In these cases, the DBA may need to push things a bit.
The DBA can give database startup an additional shove with the startup force command option. This option will use a method akin to a shutdown abort see the next section on database shutdown in order to end the current instance having difficulty before starting the new instance.
It is not recommended that the DBA use this option without extreme care, as there is usually a need for instance recovery in this type of situation.
What is the tool used for starting the Oracle database?
What connection must be used for the task? What are the five options for database startup?
Shutting Down the Oracle Database Shutting down the Oracle instance works in much the same way as starting the instance, with the requirement to cease allowing access to the database and the requirement to accomplish the task while being logged on as internal.
The task must also be accomplished from the Server Manager, either graphically with the use of the Shut Down menu under the Instance menu or with the shutdown command in line mode. The options for database shutdown are listed below: Shutdown normal Shutdown immediate Shutdown abort There are three priorities that can be specified by the DBA for shutting down the database.
The first and lowest priority is normal. It is the lowest priority because Oracle will wait for many other events to play themselves out before actually shutting down the connection. In other words, the database will make the DBA wait for all other users to finish what they are doing before the database will actually close.
The following description of events illustrates specifically how the shutdown process works under normal priority: DBA issues shutdown normal from Server Manager at 3 p.
User X is logged onto the system at and performs data entry until p. User X will experience no interruption in database availability as a result of shutdown normal.
User Y attempts to log into the database at p. User Z is the last user logged off at p. The database will now shut down. When the DBA starts the database up again, there will be no need to perform a database recovery. There are three rules that can be abstracted from this situation.
The first is that no new users will be permitted access to the system. The second is that the database does not force users already logged onto the system to log off in order to complete the shutdown. Third, under normal shutdown situations, there is no need for instance recovery. Normal database shutdown may take some time.
The time the process can take depends on several factors. Some of the factors that the database shutdown will depend on are whether many users have active transactions executing at the time the shutdown command is issued, how many users are logged on to the system and on the shutdown priority issued by the DBA. A higher-priority shutdown that the DBA can enact in certain circumstances is the shutdown immediate command. Shutting down a database with immediate priority is similar to using the normal priority in that no new users will be able to connect to the database once the shutdown command is issued.
However, Oracle will not wait for a user to logoff as it did in points 2 and 4 above. Instead, Oracle terminates the user connections to the database immediately and rolls back any uncommitted transactions that may have been taking place.
This option may be used in order to shut down an instance that is experiencing unusual problems, or in the situation where the database could experience a power outage in the near future. A power outage can be particularly detrimental to the database; therefore, it is recommended that the DBA shut things down with immediate priority when a power outage is looming. There are two issues associated with shutting down the database with immediate priority. The first is the issue of recovery.
The database will most likely need instance recovery after an immediate shutdown. This activity should not require much effort from the DBA, as Oracle will handle the recovery of the database instance itself without much intervention. However, the other issue associated with shutting down the database immediately is that the effect of the shutdown is not always immediate!
In some cases, particularly in situations involving user processes running large-volume transactions against a database, the rollback portion of the database shutdown may take some time to execute.
The final priority to be discussed with shutting down a database is the shutdown with abort priority. This is the highest priority that can be assigned a shutdown activity. In all cases that this priority is used, the database will shut down immediately, with no exceptions.
SHARED POOL Library Cache Shared SQL Area
Use of this priority when shutting down a database instance should be undertaken with care. The additional item that a shutdown abort uses to prevent the database from waiting for rollback to complete is not to roll back uncommitted transactions. This approach requires more instance recovery activity, which is still handled by Oracle. Only in a situation where the behavior of the database is highly unusual or when the power to the database will cut off in less than two minutes should the shutdown abort option be employed.
Otherwise, it is usually best to avoid using this option entirely, and use shutdown immediate in circumstances requiring the DBA to close the database quickly. What connection must be used for the task of database shutdown?
What are the three options for database shutdown? Changing Database Availability and Restricting Login During the course of normal operation on the database, the DBA may require changing the availability of the database in some way.
For example, the DBA may have to initiate emergency maintenance on the database, which requires the database to be unavailable to the users. Perhaps there are some problems with the database that need to be resolved while the instance is still running but the database is unavailable. For this and many other reasons, the DBA can alter the availability of the database in several ways. The following discussion will highlight some of those ways. The first way a DBA may want to alter the status and availability of the database instance is to change the mount status of a database.
In some situations, the DBA may need to start a database with the nomount option, as discussed earlier in the section on starting the database. After the activities that required the database not to be mounted are complete, the DBA will want to mount the database to the instance, but have the database still be closed and therefore unavailable to the users.
Oracle Architecture Diagram and Notes
To change the status of a database to be mounted, the DBA can use either the graphical interface of Server Manager to mount the database or use the alter database mount statement to achieve that effect.
Mounting the database allows the DBA to do several database maintenance activities without allowing users the chance to access the database and cause contention.
After database work, or in the course of a manual startup, the DBA will want to allow the users access to the database. This step can be accomplished in two ways.
Like mounting the database manually, the DBA can use the graphical user interface to open the database for user access. This area allows SQL execution plans to be reused by many users. LATCHES Background process needs one of the data structure to satisfy its purpose, it acquires a latch while it manipulates or looks for a shared resource.
Latches are simple types of a lock that can be very quickly acquired and freed, low-level serialization mechanisms to protect shared data structures in the system global area SGA.
For example, latches protect the list of users currently accessing the database and protect the data structures describing the blocks in the buffer cache. A server or background process acquires a latch for a very short time while manipulating or looking at one of these structures. The implementation of latches is operating system dependent, particularly in regard to whether and how long a process will wait for a latch.
Advantages of Latches It can be very quickly acquired and freed. There is a cleanup procedure that will be called if process dies while holding a latch.
Synchronization of levels of latching - Process acquires a latch at a certain level and it cannot acquire another latch subsequently that is equal to or less than that level. Prevents more than one process from executing the same piece of code at a given time. Latches have an associated level that is used to prevent deadlocks. Limitations Low-level of serialization one at a time The implementation of latches is operating system dependent, particularly in regard to whether and how long a process will wait for a latch.
Introduction to Oracle Database Memory Structures
If it acquires a latch for more time, there is a possibility process may die. There is no ordered queue of waiters like in enqueues.
Latch waiters may either use timers to wakeup and retry or spin only in multiprocessors. Since all waiters are concurrently retrying depending on the scheduler , anyone might get the latch and conceivably the first one to try might be the last one to get. Any object Not only data structures which can be concurrently non serially used, can be protected with enqueues.
A good example is of locks on tables. We allow varying levels of sharing on tables e. Enqueue is obtained using an OS specific not dependent locking mechanism. An enqueue allows the user to store a value in the lock, i.
The OS lock manager keeps track of the resources locked. If a process cannot be granted the lock because it is incompatible with the mode requested and the lock is requested with wait, the OS puts the requesting process on a wait queue which is serviced in FIFO. Advantages Allows several concurrent processes to have varying degree of known resources. If a process cannot be granted lock then it puts the process in wait queue. There is ordered queue of waiters.
Differences between Latches and Enqueues Latches - Low level of serialization. Enqueue - Concurrency. Latches - Process acquires latch for a short time and there is no ordered queue of waiters.Differences between Latches and Enqueues Latches - Low level of serialization. The cache contains default, keep, and recycle pools. To start the instance, use the startup nomount command in order to run the instance without mounting a previously existing database. That piece of information identifies a pair of facts about the relationship.
What is the tool used for starting the Oracle database? The distinct categories are single-byte character sets, multibyte character sets, and languages read from right to left.
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