F5-TTS Model Installation on Windows - Easy Step by Step Tutorial

One of the most frustrating errors DBAs face in Oracle 19c is ORA-01555: snapshot too old. Here’s a practical fix.

Cause

Undo retention is too low or undo tablespace is undersized for long-running queries.

Solution

-- Check current settings
SHOW PARAMETER undo_retention;
SELECT tablespace_name, size_in_gb FROM (
  SELECT tablespace_name, ROUND(SUM(bytes)/1024/1024/1024,2) size_in_gb 
  FROM dba_data_files GROUP BY tablespace_name);

-- Fix
ALTER SYSTEM SET undo_retention=7200 SCOPE=BOTH;   -- 2 hours

-- Resize undo tablespace
ALTER TABLESPACE UNDOTBS1 RESIZE 10G;

Pro Tip (Developer): Use /*+ RESULT_CACHE */ or smaller batch processing in long queries.