H

HA

See high availability.

HA data service

See data service.

HADB

See high availability database.

HADB node

(n.) A set of HADB processes, a dedicated area of shared memory, and one or more secondary storage devices used for storing and updating session data. Each active (data storage) node must have a mirror node; therefore nodes occur in pairs. In addition, two or more spare nodes can be included to maximize availability. If an active node fails and cannot recover within a timeout period, the spare node copies the data from the mirror node and becomes active. See also high availability database

handle

(n.) An object that identifies an enterprise bean. A client can serialize the handle and then later deserialize it to obtain a reference to the bean.

hard restart

(n.) The termination of a process or service and its subsequent restart. See also soft restart.

hashdir

(n.) A command-line utility for determining which directory contains the message store for a particular user.

HDML

(Handheld Device Markup Language) (n.) Openwave’s proprietary language to program mobile devices that use Openwave browsers.

header

(n.) The portion of an email message that precedes the body of the message. The header is composed of field names followed by a colon and then values. Headers contain information useful to email programs and to users trying to make sense of the message. For example, headers include delivery information, summaries of contents, tracing, and MIME information. Headers tell whom the message is for, who sent it, when it was sent, and what it is about. Headers must be written according to RFC 822 so that email programs can read them.

header field

(n.) A named item of information, such as “From:” or “To:”, in a message header. Also known as a header line.

heartbeat

(n.) In the Application Server, a periodic message sent to all available servers in a cluster. Lack of a heartbeat after a specified interval and number of retries might trigger failover.

heuristic decision

(n.) The transactional mode used by a particular transaction. A transaction has to either Commit or Rollback.

high availability

(n.) Enables the detection of a service interruption and provides recovery mechanisms in the event of a system failure or process fault. In addition, high availability allows a backup system to take over the services in the event of a primary system failure. Also known as HA.

high availability database

(HADB) (n.) A highly scalable, highly available session state persistence infrastructure. Application Server uses the HADB to store HTTP session states and stateful session bean states. See also HADB node, active node

home handle

(n.) An object that can be used to obtain a reference to the home interface. A home handle can be serialized and written to stable storage and deserialized to obtain the reference.

home interface

(n.) An interface that defines the methods that enable a client to create and remove an EJB 1.x or 2.x enterprise bean. The home interface of a session bean defines create and remove methods, whereas the home interface of an entity bean defines create, finder, and remove methods. See also remote interface.

home page

(n.) A document that exists on the server and acts as a catalog or entry point for the server’s contents. The location of this document is defined within the server’s configuration files.

hop

(n.) A transmission between two computers.

horizontal scalability

(n.) The Calendar Server’s capability to run on a single server or as a group of processes that are spread across multiple servers with a wide variety of possible configuration options.

host

(n.) The machine on which one or more servers reside.

hosted domain

(n.) An email domain that is outsourced to an ISP. That is, the ISP provides email domain hosting for an organization by operating and maintaining the email services for that organization. A hosted domain shares the same Java Enterprise System Messaging Server host with other hosted domains. In earlier LDAP-based email systems, a domain was supported by one or more email server hosts. With Messaging Server, many domains can be hosted on a single server. For each hosted domain, there is an LDAP entry that points to the user and group container for the domain. Also known as a virtual hosted domain or a virtual domain

host-IP authentication

(n.) A security mechanism used for limiting access to the Java Enterprise System Administration Server or the files and directories on a web site by making them available only to clients using specific computers.

host name

(n.) The name of a particular machine within a domain. The host name is the IP host name, which might be either a “short-form” host name (for example, mail) or a fully qualified host name. The fully qualified host name consists of the host name and the domain name. For example, mail.example.com is the host name mail in the domain example.com. Host names must be unique within their domains. Your organization can have multiple machines named mail, as long as the machines reside in different subdomains, for example, mail.corp.example.com and mail.field.example.com. Host names always map to a specific IP address. See also fully qualified domain name, IP address.

host-name hiding

(n.) The practice of using domain-based email addresses that do not contain the name of a particular internal host.

HTML

(hypertext markup language) (n.) A markup language for hypertext documents on the Internet. HTML enables the embedding of images, sounds, video streams, form fields, references to other objects with URLs, and basic text formatting. Each block of text is surrounded by codes that indicate the nature of the text.

HTML page

(n.) A page coded in HTML and intended for display in a web browser.

HTTP

(hypertext transfer protocol) (n.) The Internet protocol based on Transmission Control Protocol/Internet Protocol that fetches hypertext objects from remote hosts. HTTP messages consist of requests from client to server and responses from server to client.

HTTPD

(hyptertext transfer protocol daemon) (n.) An abbreviation for the HTTP daemon or service, which is a program that serves information using the HTTP protocol.

HTTP-NG

(hypertext transfer protocol-next generation) (n.) The next generation of hypertext transfer protocol.

HTTPS

(hypertext transfer protocol secure) (n.) A secure version of HTTP implemented using the secure socket layer protocol.

HTTP servlet

(n.) A servlet that extends javax.servlet.HttpServlet. These servlets have built-in support for the HTTP protocol. See also generic servlet.

hub

(n.) A host that acts as the single point of contact for the system. When two networks are separated by a firewall, for example, the firewall computer often acts as a mail hub.

hypertext transfer protocol secure

See HTTPS.