Apr 13, 2018 · Databases

Understanding MySQL ALTER Operations and Online Schema Change (OSC) Tools

This article explains the detailed steps of MySQL ALTER operations, compares single‑instance and master‑slave scenarios, introduces various online schema‑change tools such as pt‑OSC, outlines native MySQL OSC support, discusses limitations, and provides practical recommendations for safely performing large‑table DDL.

ALTEROnline Schema Changedatabase migration

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Understanding MySQL ALTER Operations and Online Schema Change (OSC) Tools

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Dec 11, 2015 · Databases

Why MySQL Replication Lags During Long ALTERs and MyISAM Locks—and How to Fix It

The article examines two common MySQL master‑slave delay scenarios—slow ALTER operations and MyISAM table‑level locks—explains why they cause replication lag, and offers practical mitigation steps such as scheduling problematic SQL, isolating lagging slaves, and tuning binlog write settings.

ALTERMaster‑SlaveMyISAM

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Why MySQL Replication Lags During Long ALTERs and MyISAM Locks—and How to Fix It