|Oracle9i Real Application Clusters Administration
Release 1 (9.0.1)
Part Number A89869-02
The alert files contain important information about error messages and exceptions that occur during Oracle database operations.
The interface (or calling conventions) that an application program accesses operating system and other services. An API is defined at the source code level and provides a level of abstraction between the application and the kernel (or other privileged utilities) to ensure the portability of the code. A typical example of an API is the Oracle Call Interface (OCI).
When you execute the Discover Node command from the Console, the Management Server contacts the Oracle Intelligent Agent installed on that node to discover the Oracle services installed on the node. The Management Server then places the new information in the repository, and updates the hierarchical tree in the Navigator window of the Console, displaying a broad view of all nodes and their respective services.
A feature that automatically manages the sizing of undo tablespaces.
The synchronization of data in multiple caches so that reading a memory location by way of any cache will return the most recent data written to that location by way of any other cache. Sometimes also called cache consistency.
A diskless cache coherency mechanism used in Real Application Clusters that provides copies of blocks directly from the holding instance's memory cache to the requesting instance's memory cache. Cache Fusion is the collective term for the group of features of the Oracle shared cache architecture in Real Application Clusters.
A cluster is a set of instances, each typically running on different nodes, that coordinate with one another when accessing the shared database residing on disk.
Cluster Manager is an operating system-dependent component that discovers and tracks the membership state of nodes by providing a common view of cluster membership across the cluster. CM monitors process health. The LMON process, a background process that monitors the health of the Global Cache Service (GCS), registers and de-registers from CM.
See: Cluster Manager (CM).
A specially formatted description of the destination for a network connection. A connect descriptor contains destination service and network route information.
The destination service is indicated by using its service name for Oracle release 8.1 databases or greater or its Oracle system identifier (sid) for Oracle release 8.0 or version 7 databases. The network route provides, at a minimum, the location of the listener through use of a network address.
A feature that balances the number of active connections among various instances and shared server dispatchers for the same service. Because of service registration's ability to register with remote listeners, a listener is always aware of all instances and dispatchers regardless. This way, a listener can sends an incoming client request for a specific service to the least loaded instance and least loaded dispatcher regardless of its location.
A file that records the physical structure of a database and contains the database name, the names and locations of associated databases and online redo log files, the timestamp of the database creation, the current log sequence number, and checkpoint information.
The Oracle Enterprise Manager Console gives you a central point of control for the Oracle environment through an intuitive graphical user interface (GUI) that provides powerful and robust system management. The Console provides menus, tool bars, and launch palettes that enable access to Oracle tools. The Console consists of four separate windows. See also: Navigator Window,Group Window, Event Management Window, and job window.
Competition for resources. The term is used in networks to describe a situation where two or more nodes attempt to access the same resource at the same time. Contention is resolved by concurrency control mechanisms.
Disk and Execution Monitor. A program that is not invoked explicitly, but lies dormant waiting for some condition to occur.
An individual responsible for the design and management of the database and for the evaluation, selection and implementation of the database management system. In smaller organizations, the data administrator and database administrator are often one in the same; however, when they are different, the database administrator's function is more technical. The database administrator would implement the database software that meets the requirements outlined by the organization's data administrator and systems analysts. DBA is also an acronym for Data Block Address.
A data file is a physical operating system file on disk that was created by Oracle. It contains data structures such as tables and indexes. A data file can only belong to one database.
See: Oracle Data Gatherer.
See: Database Administrator (DBA). Outside the context of Real Application Clusters, DBA is also an acronym for Data Block Address.
A server that requires a dedicated server process for each user process. There is one server process for each client. Oracle Net sends the address of an existing server process back to the client. The client then resends its connect request to the server address provided. Contrast with shared server.
Database and application environments that help with decision support or data warehousing systems.
A process that enables many clients to connect to the same server without the need for a dedicated server process for each client. A dispatcher handles and directs multiple incoming network session requests to shared server processes. See also shared server.
The process of recovery over a cluster.
Enqueues are shared memory structures that serialize access to database resources and are associated with a session or transaction. In Real Application Clusters, enqueues can be global to a database. Enqueues are local to one instance if Real Application Clusters is not enabled.
A tool for creating, deleting, and modifying Oracle Enterprise Manager configurations and settings.
Part of the Console. The Event Management window enables the administrator to remotely monitor critical database and system events.
A write-only global block access mode. In this mode no other access is allowed.
An extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information.
The process used to assign a number of contiguous data blocks.
The process of failure recognition and recovery.
Free list groups are sets of free lists available for use by one or more instances.
Real Application Clusters software that provides mechanisms to control the allocation and modification of Oracle resources.
Global Cache Service processes handle remote messages for the Global Cache Service (GCS). Current Real Application Clusters software provides for up to 10 Lock Manager Servers. The number of Lock Manager Servers varies depending on the amount of messaging traffic among nodes in the cluster. The LMSn handle Blocking Asynchronous Traps from the remote instance for GCS resources. For cross-instance read/write requests, the LMSn will create a consistent read version of the block and send it to the requesting instance. The LMSn also control the flow of messages to remote instances.
Global Cache Service resources are global resources that coordinate access to data blocks in the buffer caches of multiple Real Application Clusters instances to provide cache coherency.
The global database name is the full name of the database that uniquely identifies it from any other database. The global database name is of the form
The database name portion, OP, is a simple name you want to call your database. The database domain portion,
.US.ORACLE.COM, specifies the database domain where the database is located, making the global database name unique. When possible, Oracle Corporation recommends that your database domain mirror the network domain.
The global database name is the default service name of database, as specified by the
SERVICE_NAMES parameter in the
Dynamic performance views storing information about all open instances in a Real Application Clusters cluster. (Not only the local instance.) In contrast, standard dynamic performance views (
V$) only store information about the local instance.
The Global Enqueue Service coordinates enqueues that are shared globally.
The Global Enqueue Service Daemon is the resource agent process that manages requests for Global Cache Service (GCS) resources to control access to blocks. The LMD process also handles deadlock detection and remote resource requests. Remote resource requests are requests originating from another instance.
The background LMON process monitors the entire cluster to manage global resources. LMON manages instance deaths and the associated recovery for the Global Cache Service (GCS). In particular, LMON handles the part of recovery associated with global resources. LMON-provided services are also known as Cluster Group Services.
The Globalization Support architecture enables you to store, process, and retrieve data in native languages. It ensures that database utilities and error messages, sort order, date, time, monetary, numeric, and calendar conventions automatically adapt to the native language and locale.
Inter-instance synchronization mechanisms designed to provide cache coherency for Real Application Clusters. The term can refer to both Global Cache Service (GCS) resources and Global Enqueue Service (GES) resources.
Replaces OPSD. The Global Services Daemon is a component that receives requests from SRVCTL to execute administrative job tasks, such as startup or shutdown. The command is executed locally on each node, and the results are sent back to SRVCTL. GSD is installed on the nodes by default. Do not delete the GSD process.
Part of the Console. The Group window provides a customized graphical representation of key objects. It is created by the administrator.
High availability refers to systems with redundant components that provide consistent and uninterrupted service, even in the event of hardware or software failures. This involves some degree of redundancy.
A SQL*PLUS command to move from the SQL*Plus command line to the operating system command line.
A hybrid database is one that has both OLTP and Data Warehouse processing characteristics.
A parameter designating the continuation file of an iinitialization parameter file.
An instance initialization file that contains parameters unique for an instance and points to initdb_name.ora for database parameters.
A common database initialization file shared among the instance that contains database parameters.
For a Real Application Clusters database, each node within a cluster usually has one instance of the running Oracle software that references the database. When a database is started, Oracle allocates a memory area called the System Global Area (SGA) and starts one or more Oracle processes. This combination of the SGA and the Oracle processes is called an instance. The memory and processes of an instance manage the associated database's data and serve the one or more users of the database. You can connect to any instance to access information within a Real Application Clusters database.
Each instance has unique Oracle System Identifier (sid), instance name, rollback segments, and thread ID.
Instance Membership Recovery (IMR) is the method used by Real Application Clusters guaranteeing that all cluster members are functional or active. IMR polls and arbitrates the membership. Any members that do not show a heartbeat by way of the control file or who do not respond to periodic are you alive? messages are presumed dead.
Instance name represents the name of the instance and is used to uniquely identify a specific instance when multiple instances share common services names. The instance name is identified by the
INSTANCE_NAME parameter in the
The instance name is the same as the Oracle System Identifier (sid.) See also: Oracle system identifier (sid).
A number that associates extents of data blocks with particular instances. The instance number enables you to start up an instance and ensure that it uses the extents allocated to it for inserts and updates. This will ensure that it does not use space allocated for other instances. The instance cannot use data blocks in another free list unless the instance is restarted with that instance number.
You can use various SQL options with the
INSTANCE_NUMBER initialization parameter to associate extents of data blocks with instances.
The instance number is depicted by the
INSTANCE_NUMBER parameter in the instance initialization file,
See: Oracle Intelligent Agent.
The communication link between nodes.
Inter-Process Communication is an operating system-dependent component that provides the reliable transfer of messages between instances on different nodes.
Part of the Console. The Job window enables the administrator to automate repetitive activities.
A latch is a low level serialization mechanism that protects in-memory data structures in the System Global Area (SGA). Latches do not protect data files, are automatic, and are held for a very short time in exclusive mode. Because latches are synchronized within a node, they do not facilitate internode synchronization.
A protocol for accessing on-line directory services.
The listener is a separate process that resides on the server whose responsibility is to listen for incoming client connection requests and manage the traffic to the server.
The listener brokers the client request, handing off the request to the server. Every time a client (or server acting as a client) requests a network session with a server, a listener receives the actual request. If the client's information matches the listener's information, the listener grants a connection to the server.
A configuration file for the listener that identifies the listener name and protocol addresses that the listener is accepting connection requests on services it is listening for.
listener.ora file typically resides in
$ORACLE_HOME/network/admin on UNIX platforms and
%ORACLE_HOME%\network\admin on Windows NT and Windows 2000.
Oracle databases do not require identification of the database service because of service registration. However, static service configuration is required for an Oracle databases if you plan to use Oracle Enterprise Manager.
The Oracle Enterprise Manager Management Server provides centralized intelligence and distributed control between the Console and the managed nodes, and processes system management tasks sent by the Console and administers the distribution of these tasks across the enterprise. The Management Server stores all system data, application data, and information about the state of managed nodes in a repository. The repository is a set of tables stored in a database. High performance and scalability is ensured because the workload is automatically shared and balanced when there are multiple Management Servers.
A list of blocks containing available space drawn from any extent in a table.
The average time (usually expressed in hours) that a component works without failure. It is calculated by dividing the total number of failures into the total number of operating hours observed. The term can also mean the length of time a user can reasonably expect a device or system to work before an failure occurs.
The average period of time that a component will work until failure.
The average time that it takes to get a failed piece of hardware back on line. Outside the context of Real Application Clusters, the acronym MTTR is also used for Mean Time to Repair.
The component used for programmatic execution and the buffering of data.
See shared server.
The capability of having more than one Oracle home directory on a machine.
See shared server.
See: null (N).
The method used by a client application to resolve a net service name to a connect descriptor.
Part of the Console. The Navigator window contains an object browser that provides an organized, consistent, and hierarchical view of the database objects in the network.
A simple name for a service that resolves to a connect descriptor. Users initiate a connect request by passing a user name and password along with a net service name in a connect string for the desired service:
Depending on your needs, net service names can be stored in a variety of places, including:
tnsnames.ora, on each client
See Oracle Net.
A protocol developed by Sun Microsystems, and defined in RFC 1094, that allows a computer to access files over a network as if the files were on local disks.
A node is a machine where an instance resides.
Null indicates that an access mode is not assigned to a block or resource.
The processing of transactions by computers in real time.
A software layer that consists of several software components developed by vendors. The OSD layer maps the key operating system/cluster-ware services required for proper operation of Real Application Clusters.
Obsolete program. See Server Control (SRVCTL).
Obsolete product. See: Server Management (SRVM).
A tool that enables you to create, delete, and modify a database as well as add and delete instances.
The Oracle Data Gatherer collects performance statistics for the Oracle Performance Manager. The Oracle Data Gatherer is part of the part of the Oracle Intelligent Agent process. The Oracle Data Gatherer must be installed on a node somewhere on the network.
Oracle Enterprise Edition is an Object-Relational Database Management System (ORDBMS). It provides the applications and files to manage a database. All other Real Application Clusters components are layered on top of Oracle Enterprise Edition.
A system management tool that provides an integrated solution for centrally managing your heterogeneous environment. Oracle Enterprise Manager combines a graphical Console, Management Server, Oracle Intelligent Agent, repository database, and tools to provide an integrated, comprehensive systems management platform for managing Oracle products.
A product family consists of system management tools designed to efficiently manage the complete Oracle environment.
A process that runs on each of the nodes. It functions as the executor of jobs and events sent by the Console by way of the Management Server. High availability is ensured since the agent can function regardless of the status of the Console or network connections.
Oracle Net is the foundation of Oracle's family of networking products, allowing services and their applications to reside on different computers and communicate as peer applications. The main function of Oracle Net is to establish network sessions and transfer data between a client machine and a server or between two servers. Once a network session is established, Oracle Net acts as a data courier for the client and the server.
Obsolete deamon. See Global Services Daemon (GSD).
Obsolete product. See Server Management (SRVM).
An add-on application for Oracle Enterprise Manager that offers tabular and graphic performance statistics for Real Application Clusters. The statistics represent the aggregate performance for all instances running on Real Applications.
The Oracle System Identifier (sid) identifies a specific instance of the running Oracle software. For an Real Application Clusters database, each node within the cluster has an instance referencing the database.
The database name, specified by the
DB_NAME parameter in the
INITDB_NAME.ORA file, and unique thread ID make up each node's sid. The thread ID starts at 1 for the first instance in the cluster, and is incremented by 1 for the next instance, and so on. See also: instance name.
A tool to install the Oracle relational database software. You can also use the Oracle Universal Installer to launch the Oracle Database Configuration Assistant (DBCA).
A file used by the Oracle server that provide specific values and configuration settings that are used on database startup. The keyword
PFILE is used in the startup command.
A file created by the
ORAPWD command. A database must use password files if you want to connect as
SYSDBA over a network.
See: Process Monitor (PMON).
Each Oracle Enterprise Manager administrator can set up specific user names, passwords, and roles for nodes, listeners, databases, and other services that you administer in the network.
An integer used by the operating system kernel to uniquely identify a process.
A process monitor database process that performs process recovery when a user process fails. PMON is responsible for cleaning up the cache and freeing resources that the process was using. PMON also checks on dispatcher and server processes and restarts them if they have failed. As a part of service registration, PMON registers instance information with the listener.
In Real Application Clusters, if a session (reader) needs to read a data block that has been recently modified by another session in a different instance (writer), a concurrency control mechanism takes place to ensure read consistency. This mechanism involves Cache Fusion.
An architecture that allows multiple instances to access a shared database of data files. Real Application Clusters is also a software component that provides the necessary Real Application Clusters scripts, initialization files, and data files to make the Oracle Enterprise Edition and Real Application Clusters.
An Oracle tool that enables you to back up, copy, restore, and recover data files, control files, and archived redo logs. It is included with the Oracle server and does not require separate installation. You can invoke RMAN as a command line utility from the operating system (O/S) prompt or use the GUI-based Enterprise Manager Backup Manager.
Redo files contain records of all changes made to data in the database buffer cache. Every Oracle database has a set of two or more redo log files. The set of redo log files for a database is collectively known as the database's redo log. A redo log is made up of redo entries (also called redo records). Each of these is a group of change vectors describing a single atomic change to the database. The primary function of the redo log is to record all changes made to data. Should a failure prevent modified data from being permanently written to the data files, the changes can be obtained from the redo log and work is never lost. Redo log files are critical in protecting a database against failures. To protect against a failure involving the redo log itself, Oracle allows a multiplexed redo log so that two or more copies of the redo log can be maintained on different disks.
See redo log switch.
When Oracle switches from using one online archive redo log to using another. All records generated to this point are switched out and archived.
Most often a hardware architecture that combines multiple hard disk drives to allow rapid access to a large volume of stored data. You can also implement RAID as a software architecture, although this is less common.
A repository database is a set of tables in an Oracle database that stores data required by Oracle Enterprise Manager. This database is separate from the database on the nodes.
See: Recovery Manager (RMAN).
Rollback segments are records of old values of data that were changed by each transaction (whether committed or not committed.) Rollback segments are used to provide read consistency, to roll back transactions, and to recover the database. Each node typically has two rollback segments, that are identified with a naming convention of RBSthread_id_rollback_number by the
ROLLBACK_SEGMENTS parameter in the
Scalability is the ability to add additional nodes to Real Application Clusters applications and achieve markedly improved scale-up and speed-up.
A preconfigured, ready-to-use database that re quires minimal user input to create. See also: starter database.
Replaces OPSCTL. Server Management uses the SRVCTL utility (installed on each node) to manage configuration information that is used by some Oracle tools. For example, SRVCTL serves as a single point of control between the Oracle Intelligent Agent and the nodes. Only one node's Oracle Intelligent Agent is used to communicate with SRVCTL. SRVCTL on that node then communicates to the other nodes through Oracle Net.
A comprehensive and integrated system management solution for Real Application Clusters. Server Management enables you to manage multi-instance databases running in heterogeneous environments through an open client/server architecture through Oracle Enterprise Manager.
In addition to managing cluster databases, Server Management enables you to schedule jobs, perform event management, monitor performance, and obtain statistics to tune cluster databases. Note that SRVM is not a separate product. It is an integral part of Oracle Enterprise Manager.
A binary parameter file that resides on the Oracle Server. This file contains parameter settings that are both global and instance-specific. These parameter settings are persistent across instance shutdown and instance startup events.
When you execute the Discover Node command from the Console, the Management Server contacts the Oracle Intelligent Agent installed on that node to discover the Oracle services installed on the node. The Management Server then places the new information in the repository and updates the hierarchical tree in the Navigator window of the Console, displaying a broad view of all nodes and their respective services.
A Service name is a logical representation of a database. This is the way a database is presented to clients. A database can be presented as multiple services and a service can be implemented as multiple database instances. The service name is a string that is the global database name, a name comprised of the database name (
DB_NAME) and domain name (
DB_DOMAIN), entered during installation or database creation.
If you are not sure what the global database name is, you can obtain it from the combined values of the
SERVICE_NAMES parameter in the common database initialization file,
The service name is included in the
CONNECT_DATA part of the connect descriptor.
A feature whereby the Process Monitor (PMON) automatically registers information with a listener. Because this information is registered with the listener, the
listener.ora file does not need to be configured with this static information.
Service registration provides the listener with the following information:
This allows the listener to direct a client's request appropriately.
This load information allows the listener to determine which dispatcher can best handle a client connection's request. If all dispatchers are blocked, the listener can spawn a dedicated server for the connection.
See: System Global Area (SGA).
The buffer state name for shared access mode to a block.
Shared is a protected read block access mode. No writes are allowed in shared mode. In shared mode, any number of users can have simultaneous read access to a resource. See also: exclusive (X) access mode.
A server that is configured to allow many user processes to share very few server processes, so the number of users that can be supported is increased. With shared server configurations, many user processes connect to a dispatcher. The dispatcher directs multiple incoming network session requests to a common queue. An idle shared server process from a shared pool of server processes picks up a request from the queue. This means a small pool of server processes can server a large amount of clients. shared server is the opposite of dedicated server.
The binary parameter file that resides on the Oracle Server.
RMAN creates a snapshot control file to resynchronize from a read-consistent version of the control file. This is a temporary snapshot control file. RMAN only needs a snapshot control file when resynchronizing with the recovery catalog or when making a backup of the current control file.
A configuration file for the client or server that specifies:
sqlnet.ora file typically resides in the
$ORACLE_HOME/network/admin directory on UNIX platforms and in the
%ORACLE_HOME%\network\admin directory on Windows platforms.
Formerly OPSCTL. See Server Control (SRVCTL).
See: seed database.
Startup is an operating system-dependent component that provides one-time configuration to startup functionality.
SYSDBA is a special database administration role that contains all system privileges with the
ADMIN OPTION, and the
SYSOPER system privilege.
SYSDBA also permits
CREATE DATABASE and time-based recovery.
SYSOPER is a special database administration role that permits a database administrator to perform any of the following commands:
ALTER DATABASE OPEN/MOUNT,
ALTER DATABASE BACKUP,
ARCHIVE LOG, and
SYSOPER includes the
A group of shared memory structures that contain data and control information for one Oracle database instance. The SGA and Oracle processes constitute an Oracle instance. Oracle automatically allocates memory for an SGA whenever you start an instance and the operating system reclaims the memory when you shut down the instance. Each instance has only one SGA.
Each Oracle instance has its own set of online redo log groups. These groups are called a thread of online redo. In non-Real Application Clusters environments, each database has only one thread that belongs to the instance accessing it. In Real Application Clusters environments, each instance has a separate thread, that is, each instance has its own online redo log. Each thread has its own current log member.
The number of the redo thread that is to be used by the instance. The thread starts at 1 node for the first instance in the cluster, and is incremented by 1 for the next instance, and so on. Threads are declared by the
THREAD parameter in the
.ORA file. When Oracle generates redo log files, the files include the thread ID. This enables you to easily identify a particular node's log files.
A file that contains net service names. This file is needed on clients, nodes, the Console, and the Oracle Performance Manager machine.
Each server and background process can write to an associated trace file. When an internal error is detected by a process, it dumps information about the error to its trace file. Some of the information written to a trace file is intended for the database administrator, while other information is intended for Oracle Support Services. Trace file information is also used to tune applications and instances.
A list of blocks freed by uncommitted transactions.
A runtime failover for high-availability environments, such as Real Application Clusters and Oracle Real Application Clusters Guard, TAF refers to the failover and re-establishment of application-to-service connections. It allows client applications to automatically reconnect to the database if the connection fails, and optionally resume a SELECT statement that was in progress. This reconnect happens automatically from within the Oracle Call Interface (OCI) library.
A memory-based networking interface.