# Introducing the Large Hadron Migrator

DevFeed: [Introducing the Large Hadron Migrator](<https://devfeed.tech/articles/introducing-the-large-hadron-migrator-2064.md>)

Original publisher: [Read original article](<https://developers.soundcloud.com/blog//introducing-the-large-hadron-migrator-3>)

Published: 2011-05-04T00:00:00Z

Content type: article

Language: en

Sources: [SoundCloud Backstage Blog](<https://devfeed.tech/sources/soundcloud-backstage-blog.md>)

Topics: [Rails](<https://devfeed.tech/topics/rails.md>), [Database](<https://devfeed.tech/topics/database.md>), [migration](<https://devfeed.tech/topics/migration.md>), [Ruby](<https://devfeed.tech/topics/ruby.md>), [Development](<https://devfeed.tech/topics/development.md>)

Tags: [database](<https://devfeed.tech/tags/database.md>), [development](<https://devfeed.tech/tags/development.md>), [migration](<https://devfeed.tech/tags/migration.md>), [open-source](<https://devfeed.tech/tags/open-source.md>), [ruby](<https://devfeed.tech/tags/ruby.md>), [tool](<https://devfeed.tech/tags/tool.md>)

## AI overview

The article introduces Large Hadron Migrator, a Ruby gem for performing online ActiveRecord database migrations while a system remains live. It addresses table-locking problems on large Rails databases by copying data to a replacement table, using triggers and a journal table to capture concurrent changes, and replaying those changes before the tables are renamed.

## Source excerpt

Rails style database migrations are a useful way to evolve your data schema in an agile manner. Most Rails projects start like this, and at...