Glossary: Sybase Control Center for Adaptive Server

See the Adaptive Server glossary for a complete list of Adaptive Server terms.

• Adaptive Server – a server in the Sybase client/server architecture that manages multiple databases and multiple users, keeps track of the actual location of data on disks, maintains mapping of logical data description to physical data storage, and maintains data and procedure caches in memory. Sybase Control Center can manage multiple Adaptive Servers.
• alert – a mechanism for notifying administrators when a managed resource experiences a status change, or when a performance metric passes a user-specified threshold.
• alert instance – a copy of an alert type that has been configured to generate a particular kind of alert for a specific managed resource.
• alert notification – an indication that an alert has fired. Alert notifications appear in the Alert Monitor view. If e-mail notification is enabled, alert notifications are also delivered to the specified e-mail address.
• alert storm – the result of issuing many redundant alerts associated with a common or root occurrence. See also alert suppression.
• alert storm suppression – a Sybase Control Center feature that can be configured to prevent alert storms by suppressing repeat alert notifications for a specified period of time.
• alert type – (1) A template that defines the resource type and the key performance indicator associated with an alert instance. (2) The basis on which an alert fires: state or threshold. Some alerts are triggered by the state of their key performance indicator (for example, running or stopped), while other alerts are triggered when their KPI’s numerical value passes a specified threshold.
• availability – indicates whether a resource is accessible and responsive.
• blocking – waiting for a lock; a task that needs to acquire a lock on a row, page, or table must wait, or block, if another process holds an incompatible lock on its target object.
• cache – See data cache, procedure cache, or statement cache.
• chart trend peiod – the period, in minutes, over which data is displayed in historical charts. Set the chart trend period on the Settings screen of the Adaptive Server monitor. Contrast with screen refresh interval.
• collection – a named, predefined set of key performance indicators for which values are collected from monitored servers at the same time. Collections supply the performance and availability data shown on Sybase Control Center screens and charts. Use the scheduler to view a list of collections and to control which collections run, how often they run, and the length of time for which they run.
• collection repeat interval – the period, in seconds, between successive repititions of a statistics collection job. The collection repeat interval determines how often new data on historical monitoring screens is available to be refreshed. Set the collection repeat interval in the scheduler. See also screen refresh interval.
• data cache – also called buffer cache and named cache. An area of memory within Adaptive Server that contains the images of database pages and the data structures required to manage the pages. Each cache is given an unique name that is used for configuration purposes. By default, Adaptive Server has a single cache named “default data cache.” Caches configured by users are called user-defined caches.
• device – in Adaptive Server, any piece of a disk or file in the file system used to store databases and their component objects.
• engine – an instance of the Adaptive Server executable that can communicate with other Adaptive Server engines in shared memory. An Adaptive Server running on a uniprocessor machine always has one engine, engine 0. An Adaptive Server running on a multiprocessor machine can have one or more engines.
• event – an activity in the system, such as a user logging in, a service starting or stopping, or a condition changing. Use the alerts feature to detect and notify you about system events.
• heat chart – a graphical view of resource availability in the current perspective.
• index – a database object that consists of key values from data tables and pointers to the pages that contain those values. Indexes speed up access to data rows by pointing Adaptive Server to the location of a table column’s data on disk.
• job – a task performed by the scheduler in Sybase Control Center.
• key performance indicator (KPI) – a single metric used to evaluate the status or performance of a monitored resource. A KPI value can be a state (such as running, error, or stopped) or a numerical value. KPIs are grouped into collections (and also, for some product modules, into key performance areas, or KPAs). KPI values are collected by scheduled collection jobs and appear on monitoring screens and in the statistics and heat charts. Examples of KPIs are Server Availability and Number of Blocked Processes.
• lock – a concurrency control mechanism that protects the integrity of data and transaction results in a multiuser environment. Adaptive Server applies table, page, and row locks to:
  
  • Prevent two or more users from changing the same data at the same time
  • Prevent processes from reading data that is in the process of being changed
• perspective – a named tab in Sybase Control Center that displays information related to a collection of managed resources (such as servers) and a set of views associated with those resources. The views in a perspective are chosen by users of the perspective. You can create as many perspectives as you need, and customize them to monitor and manage your resources. Perspectives allow you to group resources ways that make sense in your environment—for example by location, department, or project.
• procedure cache – memory used for stored procedures, batch query plans, triggers, the statement cache, datachange tracking, query compilation, and other objects used during query execution.
• query plan – the ordered set of steps required to carry out a SQL query, complete with the access methods chosen for each table. Query plans are chosen by the Adaptive Server optimizer.
• repository – a database that stores information related to managed resources, along with user preference data, operational data, and performance statistics.
• resource – a unique Sybase product component (such as a server) or a subcomponent.
• SCC-enabled login account – a user account that has been granted privileges in Sybase Control Center by mapping appropriate Sybase Control Center roles. (Roles are typically mapped to a group to which the account belongs rather than to the account itself.) The user account and group can be native to Sybase Control Center or created in the operating system or the LDAP directory service to which Sybase Control Center authentication is delegated. You must use an SCC-enabled account to log in to Sybase Control Center.
• schedule –
  the definition of a task (such as the collection of a set of statistics) and the time interval at which Sybase Control Center executes the task.
• screen refresh interval – the period in seconds between refreshes of screens in the Adaptive Server component of Sybase Control Center. Refreshing a screen redraws it with the most recent available data. Set the screen refresh interval on the Settings screen of the Adaptive Server monitor. See also collection repeat interval.
• segment – space allocated on one or more database devices. Segments can be used to control the placement of tables and indexes on specific database devices.
• semaphore – asimple internal locking mechanism that prevents a second task from accessing the data structure currently in use. Adaptive Server uses semaphores to protect transaction logs, user log caches, and I/O devices. A semaphore is relevant only in symmetric multiprocessing (SMP) environments.
• statement cache – memory used to store computed query plans. The statement cache is part of the procedure cache.
• transaction – a set of related SQL statements that are treated as a single unit of work. To ensure consistency, if all the statements in the set cannot be executed, the changes made by the query are rolled back. The tables queried during the transaction are locked until a transaction is completed.
• Transact-SQL – the SQL dialect used in Sybase Adaptive Server.
• trend period – See chart trend period.
• view – a window in a perspective that displays information about one or more managed resources. Some views also let you interact with managed resources or with Sybase Control Center itself. For example, the Perspective Resources view lists all the resources managed by the current perspective. Other views allow you to configure alerts, view the topology of a replication environment, and graph performance statistics.
• wait event – a condition that causes an Adaptive Server process to pause and wait for another event. Common wait events are waiting for disk I/O to complete, waiting on the Adaptive Server scheduler runnable queue for a CPU to become available, and waiting for another process’s lock on a table to be released.