Oracle Database Error Solutions & DBA Guide

ORA-00020: Maximum Number of Processes Exceeded – Complete Oracle DBA Troubleshooting & Resolution Guide 🚨 Quick Production Summary Error: ORA-00020: maximum number of processes (string) exceeded Immediate Causes: Exhaustion of the database PROCESSES initialization parameter, runaway connection pooling in middleware layers, connection leaks from unclosed application sessions, or operating system process limit restrictions. The ORA-00020: maximum number of processes exceeded error is one of the most critical and disruptive alerts an Oracle Database Administrator can encounter. When this error triggers, the database refuses to accept any new connections—including administrative logins via SQL*Plus AS SYSDBA in certain severe resource-exhaustion scenarios—leaving applications offline and users locked out. Unlike intermittent query timeouts or network glitches, ORA-00020 is a hard architectural boundary. Every connection to an Oracle Database—whether it is a user...

ORA-03135: Connection Lost Contact – Complete Oracle DBA Troubleshooting & Resolution Guide 🚨 Quick Production Summary Error: ORA-03135: connection lost contact Immediate Causes: Network timeout, idle session timeout (firewall/load balancer drop), server-side crash/process termination (OOM killer), or dead connection checker misconfiguration (`SQLNET.EXPIRE_TIME`). The ORA-03135: connection lost contact error is one of the most frustrating and frequently encountered connectivity failures in Oracle Database environments. Whether you are managing high-transaction OLTP systems, reporting warehouses, or complex multi-tier enterprise applications like Oracle E-Business Suite (EBS) , this error abruptly terminates active or idle database sessions, disrupting user workflows and failing background processes. Unlike errors that prevent a connection from being established in the first place (such as ORA-12514 or ORA-12541 ), ORA-03135 occurs after a successful connecti...

All Receiving Transactions Fail with "Cannot Create Accounting Flexfield Combination" – Complete Oracle E-Business Suite R12 Troubleshooting Guide The "Cannot Create Accounting Flexfield Combination" error is one of the most common accounting validation issues encountered in Oracle E-Business Suite (EBS) , particularly within Oracle Purchasing (PO) , Oracle Inventory (INV) , Oracle Receiving (RCV) , Oracle Cost Management (CST) , and Oracle General Ledger (GL) . This error typically occurs when Oracle attempts to create or validate an Accounting Flexfield Code Combination during a receiving transaction but cannot generate a valid General Ledger account. As a result, receiving transactions fail, material cannot be received into inventory, accounting entries are not created, and downstream business processes such as inventory costing, accounts payable matching, and financial reporting may also be affected. In production environments, this issue is commo...

ORA-00904: Invalid Identifier – Complete Oracle DBA Troubleshooting Guide The ORA-00904: invalid identifier error is one of the most common SQL errors encountered in Oracle Database. It affects Oracle Database Administrators (DBAs), SQL developers, PL/SQL developers, Oracle Forms developers, Oracle APEX developers, Oracle E-Business Suite administrators, ETL developers, reporting teams, and application support engineers. ORA-00904 occurs when Oracle encounters a column name, alias, object attribute, or identifier that it cannot recognize during SQL parsing. While many administrators assume the column does not exist, the actual root cause is often more complex and may involve case-sensitive identifiers, quoted column names, invalid aliases, incorrect schema references, dynamic SQL, editioning, or application deployment issues. Before Oracle executes a SQL statement, it validates every referenced identifier against the database dictionary. If Oracle cannot resolve a refere...