Migration Study Guide

📖 Core Concepts Migration – physical movement of entities (people, animals, cells, data, etc.) from one region or system to another. International migration – movement of people across state boundaries. Host state – the receiving country in an international migration event. Minimum stay requirement – migrants must remain in the host state for a prescribed minimum period. Immigration – moving into a country to reside permanently or for an extended period. Emigration – moving out of one’s country to settle permanently or for an extended period elsewhere. Animal migration – seasonal or periodic relocation of animals between habitats. Bird migration – a subset of animal migration performed specifically by birds. Gene migration – spread of genetic material among populations (evolutionary context). Cell migration – movement of individual cells essential for development and tissue maintenance. Molecular diffusion – random motion of molecules from high‑ to low‑concentration regions. Chemical migration – in organic chemistry, a substituent group moves from one part of a molecule to another. Planetary migration – change of a satellite’s orbital parameters caused by gravitational interactions. Virtual machine (VM) migration – moving a running VM from one physical host to another. Data migration – transferring data between storage types, formats, or systems. Schema migration – incremental, reversible changes to a relational database’s schema. --- 📌 Must Remember International migration requires a minimum stay in the host state. Host state ≠ origin state; it is the destination that receives migrants. Immigration = entering a new country; Emigration = leaving one’s home country. Bird migration is animal migration, but not all animal migration involves birds. Molecular diffusion is random; chemical migration is a directed, mechanistic shift of a substituent. VM migration moves a running VM; it is distinct from simply copying a VM image. Data migration deals with content; schema migration deals with structure of a database. --- 🔄 Key Processes Data migration – Not enough information in source outline. Schema migration – Not enough information in source outline. VM migration – Not enough information in source outline. Molecular diffusion – random movement from high to low concentration (no explicit steps provided). --- 🔍 Key Comparisons Animal migration vs. Bird migration Animal migration: any species, seasonal/periodic habitat shift. Bird migration: specific to avian species; a type of animal migration. Immigration vs. Emigration Immigration: moving into a country. Emigration: moving out of a country. Data migration vs. Schema migration Data migration: transfers data between storage types/formats. Schema migration: changes the structure (tables, columns) of a relational database. Molecular diffusion vs. Chemical migration Diffusion: passive, random spread down a concentration gradient. Chemical migration: purposeful rearrangement of a substituent within a molecule. VM migration vs. Data migration VM migration: moves a running virtual machine between physical hosts. Data migration: moves static data between storage systems. --- ⚠️ Common Misunderstandings Confusing immigration with emigration – they are opposite directions, not synonyms. Assuming “migration” always means permanent relocation – many migrations (e.g., animal, VM) are temporary or reversible. Equating molecular diffusion with directed chemical migration – diffusion is random; chemical migration is a specific reaction step. Thinking the host state is the origin – the host state is the receiving country, not where the migrant started. --- 🧠 Mental Models / Intuition “Cross‑border movement” – any migration can be visualized as a source → boundary → destination diagram (people, cells, data, planets). “Stay‑long enough rule” – for international migration, picture a timer that must reach the minimum stay before the migrant is counted. “Structure vs. Content” – imagine a house: Data migration moves the furniture; Schema migration remodels the rooms. --- 🚩 Exceptions & Edge Cases Minimum stay length can vary by policy; the outline only states a requirement exists. Planetary migration occurs via gravitational forces, not via a “decision” by the satellite. Schema migration is described as reversible, unlike many other migration types that are one‑way. --- 📍 When to Use Which Use VM migration when you need to relocate a running virtual environment (e.g., load balancing, hardware maintenance). Choose data migration when moving raw data between storage media, formats, or systems. Apply schema migration when the database structure must evolve (add/drop columns, tables) while preserving existing data. Identify international migration when movement crosses state borders and a minimum stay is mandated. --- 👀 Patterns to Recognize Presence of a “source → destination” wording signals a migration concept. Boundary terms (state, host state, orbital parameters) often indicate international or planetary migration. “Minimum stay” appears only in human international migration contexts. “Reversible” is uniquely attached to schema migration in the outline. --- 🗂️ Exam Traps Choosing “immigration” for a departure – the correct term for leaving a country is emigration. Selecting “diffusion” for a directed chemical shift – diffusion is random; the directed process is chemical migration. Assuming all migrations require a host state – only international human migration mentions a host state; animal, cell, or VM migrations do not. Confusing “data migration” with “schema migration” – data migration moves content; schema migration changes database design. Believing planetary migration is a human activity – it is an astronomical phenomenon driven by gravity, not a human or biological movement.