Oracle Architecture Flashcards
What is the relationship between tablespace and datafiles?
Each tablespace is divided into one or more datafiles. It has a one to many relationship.
What constitutes an Oracle database?
Permanent files that are stored on a disk.
Files are organized into three types:
- Datafiles: hold user or system data.
- Online Redo Log Files: hold changes made to the datafile.
- Controlfiles: hold information about the physical structure of the DB.
What makes up an Oracle instance?
- Made up of a shared memory region on RAM called the SGA and background processes.
- SGA is accessible by multiple processes and stores data that is required in order to operate the instance.
- Background processes are operating system processes that have a specific responsibility within the instance.
What is SQL Plus? How can one acquire it and what kind of operations can be performed with it?
SQL Plus is a freely distributed command line tool developed by Oracle. It is used to connect to an Oracle database and can execute Oracle commands or SQL queries against the database.
Advantages of a Controlfile
The controlfile is mandatory for writing by the Oracle DB server whenever the DB is open. Without it, the DB cannot be mounted and recovery is impaired. In addition, you would need to create control files if you want to change particular setting within the control files.
Differentiate between a cluster and a grid.
- Clustering is one technology in which a grid infrastructure can be created.
- Simple clusters have static resources for specific applications by specific owners.
- Grids are dynamic resource pools shareable among many different applications and users.
- Grids have a one to many relationship with clusters.
Explain the architecture of Oracle Grid.
- Pools large numbers of servers, storage, and networks into flexible, on-demand computing resources for enterprise computing needs.
- The grid computing infrastructure continually analyzes the demand for resources and adjusts the supply accordingly.
- It also makes it possible for applications to share resources across many servers.
What is a password file and why is it needed?
Password file is a separate operating system file that is stored on the disk outside of the database. This stores the usernames and passwords for the users who have SYSDBA and SYSOPER privileges. This allows administrators to logon even when the database is closed.
Explain the difference between shared server and dedicated server architecture.
- Dedicated Server: the instance creates on server process for each connected user.
- Shared Server: a single server process will serve multiple clients.
- Certain operations can only be performed on a dedicated server.
Explain how shared server architecture works.
The user connects to a dispatcher process which is responsible for delivering SQL requests to the request queue. The incoming requests will be executed and the results will be placed in the response queue. The dispatcher will also monitor the response queue and deliver the results to the relevant client. There are multiple shared server processes and dispatcher process in this architecture.
What are the instance parameters that are used for configuring shared server architecture?
- Dispatchers: astring value used to configure dispatchers.
- Shared_Servers: minimum # of shared server processes that will be present. Created during startup.
- Max Shared_Servers: max # of shared server processes.
- Shared_Server Sessions: max # of sessions that can exist simultaneously.
- Circuits: max # of virtual circuits that can exist.
Explain how the DBWn process works.
Responsible for writing dirty buffers to the disk. This occurs when a server process wants to update a data block. It will read the block from the disk to the buffer cache if it is not already in the buffer cache and then update the copy in the buffer cache.
Explain the properties of datafiles.
Datafiles and databases have a one to one relationship. Once they are created, the size cannot be altered.
What do you mean by redo log?
The redo log is the most crucial for recovery operations. It consists of two or more pre-allocated files that store all changes made to the database.
Main function(s) of the redo log.
The main function of the redo log is to store all changes made to the DB in real time.
