IT glossary: Technical terms – J
This time, our ‘IT glossary’ section focuses on technical terms from the world of hardware and IT that begin with the letter J.
#1: JBOD
What is JBOD? JBOD is the abbreviation for ‘Just a Bunch of Disks’. The term describes a cost-effective and flexible storage solution in which several hard disks are combined in one enclosure (chassis/array) without using RAID. This type of storage is suitable for simple expansions as an inexpensive and fast solution. For critical data or productive systems, however, a less risky option with better reliability should be considered. Since there is no RAID, there is no mirroring, no parity and no striping – the data is simply stored on the respective disks. If one of them fails, the data is lost. One advantage, however, is that the individual HDDs can also be used more flexibly, as they can be addressed independently of each other. Some systems also allow so-called ‘spanning’, in which the capacities of several disks are combined into a logical volume.
#2: Jumper
What is a jumper? A jumper is a small plastic connector with a conductive metal core that is placed on two or more pins of a pin header. When plugged in, an electrical contact is established that activates or deactivates certain functions or settings of a hardware component. Jumpers were often used on motherboards, hard drives or expansion cards to set configurations such as master/slave operation, voltage selection or reset options. In the past, IDE/PATA disks, for example, were ‘jumpered’ to determine which was the master and which was the slave disk in the system. On motherboards, jumpers were used to set the CPU frequency, the front side bus or the power supply. Today, these settings are usually made via the BIOS/UEFI or special software.
#3: Java
What is Java? Java is a universal, platform-independent, object-oriented programming language and the basis for many enterprise, web and mobile applications. James Gosling developed Java in 1995 at Sun Microsystems – today it is maintained by Oracle. What makes this programming language special is that it is object-oriented, strongly typed and uses a virtual machine (JVM). Once written, a programm can run on Windows, Linux, macOS or Android, as long as a JVM is available (‘write once, run anywhere’). Typical areas of application for Java include mobile apps, web applications (backend systems, frameworks), enterprise software for banks, insurance companies or large enterprises, as well as cloud and IoT environments.
#4: Joule
What is a joule? The joule (symbol: J) describes the amount of energy required to achieve a specific physical effect. One joule corresponds to the work done when a force of 1 newton acts along a distance of 1 metre. It also corresponds to the energy converted when 1 watt of power is applied for 1 second. Electrical energy (e.g. the power of a light bulb per second consumed), mechanical work (e.g. lifting a weight over a certain distance) or heat (e.g. the amount of energy required to heat a substance) are expressed in joules. Since a joule is a very small unit, larger values are often expressed in kilojoules (kJ) or megajoules (MJ).
#5: Junk
What is Junk? The term ‘junk’ comes from English and can be translated as ‘rubbish’ or “trash”. In IT, this word is mostly used as a short form for ‘junk folder’ or ‘junk mail’ – i.e. unwanted, mass-received emails containing advertising or spam. Junk mail (also known as spam mail) is often detected by spam filters and automatically moved to the junk folder. There are also terms such as ‘junk files’ or ‘junk data’, which refer to temporary and superfluous files on a PC (such as cache residues or installation files) as well as data garbage in databases or on the system.
#6: Jailbreak
What is a jailbreak? Literally translated, ‘jailbreak’ means prison escape. In IT, it refers to the removal of manufacturer restrictions, e.g. on a smartphone or tablet, in order to gain root access, make system changes or install apps that are not normally permitted. The security and usage restrictions of an operating system are circumvented in order to break free from the ‘prison’ of the manufacturer's specifications and gain full access to the system files and settings. Legally, this is a grey area: in many countries, jailbreaking is not directly illegal, but it violates the manufacturer's terms of use. In addition, you lose the manufacturer's warranty, unauthorised software can lead to crashes or malfunctions, and security gaps arise that facilitate malware and data misuse. Since iPhones and iPads were mainly ‘jailbroken’ in the past, the term is particularly common for these systems, while ‘rooting’ is often used for Android.
#7: Journaling
What is Journaling? Similar to keeping a diary, ‘journaling’ in IT refers to a process in which changes to a file system are first recorded in a journal (log) before being permanently written to the actual data structures. The journal serves as a security mechanism to ensure the consistency of the file system after crashes or power failures. The advantage: after a system crash, the data can be checked and quickly restored using the log. However, this ‘double writing’ also causes performance losses, as it reduces speed and creates additional storage requirements.
#8: Jumbo Frames
What are Jumbo Frames? Jumbo frames are Ethernet frames (i.e. the basic building blocks of data transmission in Ethernet networks) that are larger than the standard maximum size of 1,500 bytes. Jumbo frames typically have a size of up to 9,000 bytes and are used in networks that need to transport large amounts of data particularly efficiently. This means that fewer frames need to be sent, which reduces the CPU load and increases network performance. The advantage: less overhead (protocol/CPU load decreases), higher efficiency (e.g. for backups, storage networks, virtualisation) and better performance (e.g. through iSCSI or NFS). The disadvantage is that all devices in the network must support jumbo frames, misconfigurations can lead to packet loss and performance drops, and jumbo frames are not useful everywhere. Jumbo frames are used primarily in SAN environments, high-performance computing, server clusters, and backup and data replication.
#9: JVM (Java Virtual Machine)
What is a JVM? The JVM (Java Virtual Machine) is a runtime environment that executes Java programmes. It translates the platform-independent bytecode generated by the Java compiler into machine-specific instructions. This allows Java programmes to run on different operating systems without having to be recompiled. The JVM forms an abstraction layer, i.e. an intermediate layer between the programme and the operating system, to ensure platform independence. Security mechanisms are also checked and unsafe operations are prevented. The advantage: programmes do not have to be rewritten for each operating system, but run stably on different platforms.
#10: Job Queue
What is a job queue? This term refers to a ‘queue’ in which tasks (jobs) are lined up and managed until they are processed by a system or process. This job queue ensures that resources are used efficiently and that the order of execution is optimally controlled. Print jobs or database queries can be organised according to specific rules such as ‘first in, first out’, priority or scheduling. Multiple jobs can be processed sequentially or in parallel without overloading the system. In addition, administrators can see which jobs are pending and how they are prioritised. Typical areas of application include batch jobs and background processes in the operating system, print jobs, queries or transactions in a database, and tasks between services.
More explanations for anyone curious about IT can be found here 😊:
