https://www.oraclescripts.com/tags/alter-index/Recent content in ALTER INDEX on Oracle ScriptsHugo -- gohugo.ioenOracleScripts.comSat, 06 Jun 2026 00:00:00 +0000https://www.oraclescripts.com/post/oracle-index-rebuild-coalesce-alter-index/Sat, 06 Jun 2026 00:00:00 +0000https://www.oraclescripts.com/post/oracle-index-rebuild-coalesce-alter-index/ <h2 id="oracle-index-rebuild-and-coalesce-with-alter-index">Oracle Index Rebuild and Coalesce with ALTER INDEX</h2> <h2 id="purpose">Purpose</h2> <p>Over months of heavy delete and update activity, a B-tree index can accumulate empty and half-full leaf blocks. The index keeps working, but it grows wider than the data it points to, so range scans read more blocks than they need and the segment holds space that is no longer doing useful work. <code>ALTER INDEX ... REBUILD</code> and <code>ALTER INDEX ... COALESCE</code> are the two commands that address this — one rebuilds the index from scratch, the other merges adjacent sparse leaf blocks in place.</p>