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Oracle® Application Server Web Cache Administrator's Guide
10g Release 2 (10.1.2) B14046-04 |
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Oracle® Application Server Web Cache Administrator's Guide
10g Release 2 (10.1.2) B14046-04 |
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access log
A log file that contains information about the HTTP requests sent to OracleAS Web Cache for a Web site. The access log has a file name of access_log and is stored by default in $ORACLE_HOME/webcache/logs and ORACLE_HOME\webcache\logs on Windows.
admin server process
An OracleAS Web Cache process that provides administration, configuration, and monitoring capabilities.
application Web server
An origin server that manages data for a Web site, controls access to that data, and responds to clients requests. The application on the Web server interfaces with the database and performs the job requested by the Web server.
auto-restart
A mechanism that checks if the cache server process is running and automatically restarts the cache server process if it is not running.
cache cluster
A loosely coupled collection of cooperating OracleAS Web Cache cache instances working together to provide a single logical cache. This configuration is also known as OracleAS Cluster (Web Cache). Cache clusters provide failure detection and failover of caches, increasing the availability of your Web site.
cache cluster member
An instance of OracleAS Web Cache configured with other instances of OracleAS Web Cache to operate as one logical cache. The cache cluster members communicate with one another to request cacheable content that is cached by another cache cluster member and to detect when a cache cluster member fails.
cache hierarchy
A deployment in which an OracleAS Web Cache caches content from another OracleAS Web Cache to a local market. OracleAS Web Cache provides support for a distributed cache hierarchy in a distributed network and an ESI cache hierarchy in an ESI provider site configuration.
cache hit
An HTTP or HTTPS request that can be served from objects stored in the OracleAS Web Cache cache without going to the origin server.
cache miss
An HTTP or HTTPS request that cannot be served from the cache and must be forwarded to an origin server.
cache server process
An OracleAS Web Cache process that manages the cache by providing connection management and request processing.
capacity
For origin servers, the maximum number of concurrent connections that the origin server can accept.
For cache clusters, the absolute capacity for the number of concurrent incoming connections to this cache cluster member from all other cache cluster members, and the relative capacity of the cache cluster member.
category cookie
A cookie that enables the multiple version of the same page to served to different categories of users.
central cache
In a distributed cache hierarchy, an OracleAS Web Cache server that acts as an origin server to at least one remote cache. When content becomes invalid, the central cache propagates the invalidation request to the remote caches to ensure consistency.
cookie
A packet of state information sent by an origin server to a Web browser during an HTTP request. During subsequent HTTP requests, the cookie is passed back to the origin server, enabling the origin server to remember the state of the last transaction.
distributed cache hierarchy
A cache hierarchy in which a central cache acts as an origin server to a remote cache.
Domain Name System (DNS)
A system for naming computers and network services that is organized into a hierarchy of domains. DNS is used in TCP/IP networks to locate computers through user-friendly names. DNS resolves a friendly name into an IP address, which is understood by computers.
embedded URL parameter
Parameter information embedded in the URL of objects. OracleAS Web Cache accepts requests that use the following characters as delimiters: question mark (?), ampersand (&), dollar sign ($), or semi-colon (;).
ESI cache hierarchy
A cache hierarchy in which a provider cache acts as an origin server to a subscriber cache.
ESI provider site
A site that OracleAS Web Cache contacts for Edge Side Includes (ESI) assembly only. Browsers are not allowed to request content from these sites.
event log
A log file that contains OracleAS Web Cache event and error information. The event log has a file name of event_log and is stored in $ORACLE_HOME/webcache/logs on UNIX and ORACLE_HOME\webcache\logs on Windows.
expiration
A function that marks objects as invalid after a certain amount of time in the cache. When objects are marked as invalid and a client requests them, they are either immediately removed and refreshed or refreshed based on when the origin server can refresh them.
Extended Log Format (XLF)
An improved format for HTTP server logins since it is extensible, permitting a wider range of data to be captured. XLF enables you to configure the logger to generate different statistics of HTTP requests such as the IP address of clients, methods of the HTTP requests and response headers such as user agent and accept.
Extensible Markup Language (XML)
A language that offers a flexible way to create common information formats. XML is used for invalidation messages and responses.
failover
When an origin server fails, OracleAS Web Cache automatically distributes the load over the remaining origin servers and polls the failed origin server for its current up/down status until it is back online. In a cache cluster environment, OracleAS Web Cache transfers ownership of the content of the failing member to the remaining cluster members.
failure detection
In a cache cluster environment, OracleAS Web Cache detects when a cache cluster member is unavailable.
GET method
An HTTP request method used for simple requests for Web pages. A GET method is made up of a URL. Requests for pages that use the GET method are typically cached.
GET method with query string
An HTTP request method made up of a URL and a query string containing parameters and values. An example of an HTTP GET with query string follows.
http://www.myserver.com/setup/config/navframe?frame=default
This request executes a script named navframe in the /setup/config directory of the www.myserver.com server and passes the script a value of default for the frame variable.
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Note: You should not cache pages withGET with query strings forms that make changes to the origin server or database. You should only cache pages that use GET with query strings if they are used in searches.
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garbage collection
An OracleAS Web Cache process that removes stale objects based on popularity and validity.
HTTP protocol
Hypertext Transfer Protocol. A protocol that provides the language that enables browsers and the origin server to communicate.
HTTP request header
A header that enables Web browsers to pass additional information about the request and about itself to the origin server.
HTTP request method
A method included in the HTTP request that specifies the purpose of the client's request. HTTP supports many methods, but the ones that concern caching are GET, GET with query string, and POST methods.
HTTPS protocol
Secure Hypertext Transfer Protocol. A protocol that uses the Secure Sockets Layer (SSL) to encrypt and decrypt user page requests as well as the pages that are returned by the origin server.
invalidation
An OracleAS Web Cache function that marks objects as invalid. When objects are marked as invalid and a client requests them, they are removed and then refreshed with new content from the origin server. Invalidation keeps the OracleAS Web Cache cache consistent with the content on the origin servers.
invalidation coordinator
In a cache cluster environment, OracleAS Web Cache propagates invalidation messages to other cache cluster members. It sends the invalidation messages to one cache cluster member who acts as the coordinator. The coordinator propagates the invalidation messages to the other cluster members.
IP address
Used to identify a node on a network. Each computer on the network is assigned a unique IP address, which is made up of the network ID, and a unique host ID. This address is typically represented in dotted-decimal notation, with the decimal value of each octet separated by a period, for example 144.45.9.22.
load balancing
A feature in which HTTP requests are distributed among origin servers so that no single server is overloaded.
Layer 4 (L4) switch
A networking switch that operates at Layer 4 of the Open Systems Interconnection (OSI) model—the Transport layer. L4 switches base their switching decisions on the TCP/IP protocol header and determine, based on the port number, where to pass traffic.
Layer 7 (L7) switch
A networking switch that operates at Layer 7 of the OSI model—the Application layer. L7 switches base their switching decisions on URL content.
load balancer
A network switch that balances the load of incoming browser request. In an OracleAS Web Cache deployment, the load balancer is typically positioned in front of the OracleAS Web Cache server.
on-demand content
In a cache cluster environment, on-demand content consists of popular objects that are stored in the cache of each cluster member.
Open Systems Interconnection (OSI)
A model of network architecture developed by ISO as a framework for international standards in heterogeneous computer network architecture.
The OSI architecture is split among seven layers, from lowest to highest:
1. Physical layer
2. Data link layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer
Each layer uses the layer immediately following it and provides a service to the preceding layer.
Oracle Enterprise Manager
A tool for administering Oracle Application Server. It is a complete management solution for administering, configuring, and monitoring the application server and its components. Using it, you can:
View the overall status of OracleAS Web Cache
View performance metrics
Oracle Process Manager and Notification (OPMN) Server
Oracle Process Manager and Notification (OPMN) Server manages Oracle Application Server processes, including Oracle HTTP Server, OC4J, and OracleAS Web Cache processes, and channels all notifications from different components instances to all interested in receiving them. OPMN enables you to administer the OracleAS Web Cache processes, including the admin server process and cache server process.
OracleAS Web Cache Manager
A tool that combines configuration abilities with component control to provide an integrated environment for configuring and managing OracleAS Web Cache.
origin server
A server that is either an application Web server for internal sites or a proxy server for external sites outside a firewall.
owned content
In a cache cluster environment, content that is owned by a particular cache cluster member. OracleAS Web Cache distributes the cached content among the cache cluster members. In effect, it assigns content to be owned by a particular cache cluster member.
partial page caching
A feature that enables OracleAS Web Cache to independently cache and manage fragments of HTML objects. A template page is configured with Edge Side Includes (ESI) markup tags that tell OracleAS Web Cache to fetch and include the HTML fragments. The fragments themselves are HTML files containing discrete text or other objects.
performance assurance heuristics
Heuristics that enable OracleAS Web Cache to assign a queue order to objects. These heuristics determine which objects can be served stale and which objects must be retrieve immediately. While objects with a higher priority are retrieved first, objects with a lower priority are retrieved at a later time.
The queue order of objects is based on the popularity of objects and the validity of objects assigned during invalidation. If the current load and capacity of the origin server is not exceeded, then the most popular and least valid objects are refreshed first.
personalized attribute
Pages that contain personalized attributes, such as personalized greetings like "Hello, Name," icons, addresses, or shopping cart snippets, on an otherwise generic page. You can configure OracleAS Web Cache to substitute values for personalized attributes based on the information contained within a cookie or an embedded URL parameter.
popularity
The number of requests for an object since entering the cache and the number of recent requests for the object.
POST method
An HTTP request method used for requests that modify the contents of the data store on the origin server, such as posting a message to a mailing list, submitting forms for registration purposes, or adding entries to the database.
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Note: You should not cache pages withPOST forms that make changes to the origin server or database. You should only cache pages that use POST forms if they are used in searches.
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proxy server
An origin server that substitutes for the real server, forwarding client connection requests to the real server or to other proxy servers. Proxy servers provide access control, data and system security, monitoring, and caching.
provider
Set of content—content areas, pages, applications, even data from outside sources—brought together in one central location and accessed through a common interface, called a page.
provider cache
In an ESI cache hierarchy, an OracleAS Web Cache server that locally caches content for a provider site. A subscriber cache then contacts the provider caches for assembly of HTML fragments. When content becomes invalid, the provider cache propagates the invalidation request to the subscriber cache to ensure consistency.
regular expression
OracleAS Web Cache supports the POSIX 1003 extended regular expressions for URLs, as supported by Netscape Proxy Server 2.5.
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See Also: http://www.cs.utah.edu/dept/old/texinfo/regex/regex_toc.html for regular expression syntax
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remote cache
In a distributed cache hierarchy, an OracleAS Web Cache server that caches content from a central cache to serve local requests. When an invalidation request is sent to the central cache, the central cache propagates the request to the remote cache, ensuring consistent content.
reverse proxy server
A proxy server that appears to be a normal server to browsers but internally retrieves its objects from other backend origin servers as a proxy. A reverse proxy acts a gateway to the origin servers.
round robin
A method of managing server congestion by distributing connection loads across multiple servers. Round robin works on a rotating basis in that the first origin server in the list of configured servers receives the request, then the second origin server receives the second request, and so on.
Secure Sockets Layer (SSL)
A protocol developed by Netscape Corporation. SSL is an industry-accepted standard for network transport layer security. SSL provides authentication, encryption, and data integrity, in a public key infrastructure (PKI). By supporting SSL, OracleAS Web Cache is able to cache pages for HTTPS protocol requests.
selectors
OracleAS Web Cache uses selectors to filter through the caching rules to locate the appropriate rule for the request. Cacheability can be evaluated against the following selectors:
Expression type
URL expression
HTTP request method of objects
Embedded URL and POST body parameters
Body of an HTTP POST method
session binding
The process of binding a user session to a given origin server in order to maintain state for a period of time.
session-encoded URLs
HTML hyperlink tags, such as <A HREF=...>, that contain embedded session information to distinguish users. You can configure OracleAS Web Cache to substitute the values of session parameters in HTML hyperlink tags with the session information contained within a session cookie or an embedded URL parameter.
subscriber cache
In an ESI cache hierarchy, an OracleAS Web Cache server that assembles ESI content by contacting a provider cache for the template's HTML fragments. The HTML fragments are then assembled. When provider site content becomes invalid, the provider site propagates the invalidation request to the subscriber cache to ensure consistency.
Uniform Resource Locator (URL)
A standard for specifying the location and route to a file on the Internet. URLs are used by browsers to navigate the World Wide Web and consist of a protocol, domain name, directory path, and the file name. For example, http://www.oracle.com/technology/index.html specifies the location and path a browser will travel to find the main page of the Oracle Technology Network site on the World Wide Web.
virtual host site
A site hosted by OracleAS Web Cache. Browsers can request cached content from these sites through OracleAS Web Cache. In addition to caching content, OracleAS Web Cache can also assemble ESI fragments from these sites.
wallet
A transparent database used to manage authentication data such as keys, certificates, and trusted certificates needed by SSL. A wallet has an X.509 version 3 certificate, private key, and list of trusted certificates.
weighted available capacity
The percentage of the available capacity that the origin server can accept.
webcachectl utility
A utility used to start, stop, and restart the admin server process, the cache server process, and the auto-restart process, if OracleAS Web Cache is running in a standalone environment (that is, you installed OracleAS Web Cache from a kit that included only this product; you did not install OracleAS Web Cache as part of an Oracle Application Server installation).
However, beginning with OracleAS Web Cache 10g (9.0.4), when OracleAS Web Cache is installed as part of an Oracle Application Server installation, you must use OPMN to start, stop, and restart the processes. See Oracle Process Manager and Notification (OPMN) Server.
