H

HA (High Availability)

Database. High Availability. Local disk failover or shared disk failover. See High Availability of Data Nodes With Failover in Scalability, Availability, and Failover. See also Disaster Recovery (DR).

Hadoop MapReduce

Hadoop. An Apache Software Foundation software framework for reliable, scalable, distributed parallel processing of large data sets across multiple hosts. The Hadoop core framework includes a shared file system (HDFS), a set of common utilities to support distributed processing, and an implementation of the MapReduce programming model.

harmonization

The process of transforming data from disparate sources into a common, model-based representation. See also flow and Harmonize flow.

Harmonize flow

MarkLogic. The type of flow that creates a canonical model of your data using only the parts you need and leaving the rest of the data as-is. The harmonize flow is the most common type of flow in Data Hub (DH) and is typically run in batches. See flow and About Flows in the Data Hub documentation.

HDFS (Hadoop Distributed File System)

Hadoop. The Hadoop filesystem, which can be used as an input source or an output destination in jobs. HDFS is the default source and destination for Hadoop MapReduce jobs.

heartbeat

MarkLogic. Each node in a cluster communicates with all of the other nodes in the cluster at periodic intervals. This periodic communication, known as a heartbeat, circulates key information about host status and availability between the nodes in a cluster. Through this mechanism, the cluster determines which nodes are available and communicates configuration changes with other nodes in the cluster. If a node goes down for some reason, it will stop sending heartbeats to the other nodes in the cluster.

High Performance

MarkLogic. The server is designed to maximize speed and scale. Many MarkLogic applications compose advanced queries across terabytes of data that make up many millions of documents and return answers in less than a second.

historical data

Database. Data that is less critical for the lowest-latency queries than active data, but still requires online access for queries. Historical data is not typically updated.

history

Query Console. A record of previously executed versions of a query. Each time you execute a query in Query Console, its query text is saved in the history. Use the history to restore a query to a previous state.

host

MarkLogic. A host is an instance of MarkLogic Server. A host is not configured individually, but as part of a group. Forests are created on a host and added to a database to interact with HTTP, ODBC, and XDBC Servers running on the same or other hosts. Hosts can be added to a cluster. Each host in a cluster may be referred to as a node, and is usually configured for one of two types of operations; evaluation (e-node) or data management (d-node). See group, forest, HTTP Server, ODBC Server, and XDBC Server.

host group

MarkLogic. A group of one or more MarkLogic Server objects. See Groups in Administrate MarkLogic Server. See also group.

HSM (hardware security model)

Security. A hardware security module is a physical device used to safeguard and manage encryption keys. See Encryption at Rest in Secure MarkLogic Server for more information.

HTML (Hypertext Markup Language)

HTML. A standardized markup language used for tagging text files to format the look and hyperlinks for web pages on the Web.

HTTP (Hypertext Transfer Protocol)

Web. An application protocol for distributed, collaborative, hypermedia information systems, the underpinning of data communication for the World Wide Web. Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text. HTTP is the protocol to exchange or transfer hypertext.

HTTP Server

MarkLogic. MarkLogic HTTP servers can access server-side XQuery, JavaScript, and REST (Representational State Transfer) programs via web applications. You can write web applications to connect sets of XML or JSON content, and the applications can return XHTML, XML, or JSON content to a browser or other HTTP-enabled client application. HTTP servers execute code, either from a specified location on the file system or from a Modules database