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ORA-01017 invalid username password error showing Oracle authentication architecture, password hashing versions, and troubleshooting workflow for Oracle 19c/21c databases

ORA-01017: Invalid Username/Password – Complete Guide

Posted on by Sanjeeva Kumar

Last Updated: December 2025 | Oracle 19c/21c | By Ahaaryo Oracle Version Scope: This guide covers Oracle 19c (fully supported) and Oracle 21c (Innovation Release, already desupported but widely deployed). Introduction “The password is definitely correct!” – Every DBA has said this at least once while troubleshooting ORA-01017 invalid username password. I remember a production Read more about ORA-01017: Invalid Username/Password – Complete Guide[…]

Migrating Oracle 19c Database from Local Storage to ASM: A Complete Step-by-Step Guide

Posted on by Sanjeeva Kumar

Last Updated: December 2025 | Oracle 19c | ASM Grid Infrastructure Migrating an Oracle 19c CDB from local storage to ASM has six viable methods — and choosing the wrong one means unnecessary downtime or a failed rollback. This guide documents the complete migration of a production CDB with one PDB: datafiles, controlfiles, redo logs, Read more about Migrating Oracle 19c Database from Local Storage to ASM: A Complete Step-by-Step Guide[…]

Oracle ASM 19c architecture diagram showing containerized databases using Oracle ASM for shared storage management with disk groups

Oracle ASM 19c Installation: Complete Guide to Oracle Restart Grid Infrastructure [2025]

Posted on by Sanjeeva Kumar

Last Updated: December 10, 2025Tested On: Oracle Enterprise Linux 9.5, Oracle ASM 19c Patch 25 CRS-4535: Cannot communicate with Cluster Ready Services. That error at 2 AM — after a reboot — means ASM didn’t come up. Which means your databases didn’t mount. Which means your phone doesn’t stop ringing. This guide walks through Oracle Read more about Oracle ASM 19c Installation: Complete Guide to Oracle Restart Grid Infrastructure [2025][…]

data pump import date format error ORA-01843 RMAN fix Oracle 19c

How to Export NLS_DATE_FORMAT in Oracle: Data Pump Import Date Format Fix

Posted on by Sanjeeva Kumar

The Problem: Data Pump Import Fails with Date Format Error Setting NLS_DATE_FORMAT before impdp is the standard fix for data pump import date format error i.e. ORA-01843 and ORA-01861 during Data Pump imports — but it doesn’t always work. Data Pump spawns its own worker processes and doesn’t always inherit the OS-level environment. When the Read more about How to Export NLS_DATE_FORMAT in Oracle: Data Pump Import Date Format Fix[…]

Oracle Index Unique Scan — B-tree path from root to single rowid

Optimizer Access Paths: index unique scan

Posted on by Sanjeeva Kumar

Index unique scan is the fastest access path Oracle’s optimizer can choose — it returns exactly one row using a single B-tree traversal, with zero ambiguity. If you see INDEX UNIQUE SCAN in an execution plan, that part of the query is already optimal. This post shows the execution plan on a primary key lookup, Read more about Optimizer Access Paths: index unique scan[…]

Oracle direct path read buffer cache bypass PGA

Oracle Direct Path Read: Complete Performance Guide with Real Examples

Posted on by Sanjeeva Kumar

Oracle direct path read fires when the optimizer decides a full table scan should bypass the buffer cache and read directly into PGA memory. Seeing it as a top wait event in AWR doesn’t automatically mean a problem — but understanding the threshold, the parameters, and the monitoring queries determines whether it’s working for you Read more about Oracle Direct Path Read: Complete Performance Guide with Real Examples[…]

Drop a database

Posted on by Sanjeeva Kumar

There are times when you require to drop your existing database for more than one reason.  Dropping a database is not a tough job at all, if you are very sure that which database you should drop. Originally written for Oracle 11g. The DROP DATABASE command syntax and prerequisites remain the same in Oracle 12c, Read more about Drop a database[…]

Oracle Data Pump evolution timeline from legacy exp/imp utility in 9i through modern Data Pump in Oracle 19c

Data Pump: a tool to backup and restore database

Posted on by Sanjeeva Kumar

Among various techniques of backing up your database Oracle provides data pump as one of tool which they are constantly improving and making this tool sharper release by release. Data Pump was introduced in Oracle 10g as a replacement for exp/imp. This post covers the concepts that remain valid through Oracle 19c and 21c. For Read more about Data Pump: a tool to backup and restore database[…]