DEV Community

umzzil nng
umzzil nng

Posted on • Originally published at oraerror.com

Oracle ORA-00445 Error: Causes and Solutions Complete Guide

#oracle #database #dba #sql

ORA-00445: Background Process Did Not Start After Wait

ORA-00445 is a critical Oracle error that occurs during database instance startup when one or more mandatory background processes (such as PMON, SMON, DBWR, or LGWR) fail to initialize within the expected wait period. This error prevents the Oracle instance from completing its startup sequence, leaving the database unavailable. It is most commonly caused by insufficient OS resources, misconfigured kernel parameters, or incorrect initialization parameters.

Top 3 Causes and Fixes

Cause 1: Insufficient OS Kernel Parameters (Shared Memory / Semaphores)

Oracle background processes rely heavily on OS-level IPC resources including shared memory segments and semaphores. When kernel parameters like shmmax, shmall, or sem are set below Oracle's minimum requirements, background processes cannot acquire the resources they need to start.

Diagnosis:

-- Check current SGA allocation
SELECT NAME, VALUE / (1024*1024) AS SIZE_MB
FROM V$SGA;

-- Check key initialization parameters
SELECT NAME, VALUE
FROM V$PARAMETER
WHERE NAME IN ('sga_target', 'sga_max_size', 'processes', 'sessions');
Enter fullscreen mode Exit fullscreen mode

Fix: Update /etc/sysctl.conf on Linux with Oracle-recommended values, then apply with sysctl -p. After adjusting, restart the instance:

SHUTDOWN ABORT;
STARTUP;
Enter fullscreen mode Exit fullscreen mode

Cause 2: OS Resource Exhaustion (Memory or Process Limit)

If the server is running low on physical RAM, swap space, or has hit the maximum process limit (ulimit -u), Oracle cannot fork new background processes, resulting in ORA-00445. This is especially common on servers hosting multiple Oracle instances.

Diagnosis:

-- Check current process count vs. maximum allowed
SELECT NAME, VALUE AS MAX_PROCESSES,
       (SELECT COUNT(*) FROM V$PROCESS) AS CURRENT_PROCESSES,
       ROUND((SELECT COUNT(*) FROM V$PROCESS) / VALUE * 100, 2) AS PCT_USED
FROM V$PARAMETER
WHERE NAME = 'processes';
Enter fullscreen mode Exit fullscreen mode

Fix: Reduce the PROCESSES parameter or free up OS resources, then restart:

-- Reduce processes parameter if set too high
ALTER SYSTEM SET PROCESSES = 300 SCOPE = SPFILE;

SHUTDOWN IMMEDIATE;
STARTUP;
Enter fullscreen mode Exit fullscreen mode

Cause 3: Incorrect Initialization Parameters or Corrupt SPFILE

Misconfigured parameters such as an oversized SGA_TARGET exceeding physical memory, or a corrupt SPFILE, can cause background processes to fail at startup. Always verify the alert log first to identify which process failed.

Diagnosis:

-- Find alert log location
SELECT VALUE FROM V$DIAG_INFO WHERE NAME = 'Diag Trace';

-- Check component registry status
SELECT COMP_NAME, STATUS, VERSION
FROM DBA_REGISTRY
ORDER BY COMP_NAME;
Enter fullscreen mode Exit fullscreen mode

Fix: Start using a minimal PFILE to bypass SPFILE corruption:

-- Generate a PFILE from the current SPFILE
CREATE PFILE = '/tmp/init_recovery.ora' FROM SPFILE;

-- Start with the PFILE after editing problematic parameters
STARTUP PFILE = '/tmp/init_recovery.ora';

-- Recreate SPFILE once the instance is stable
CREATE SPFILE FROM PFILE = '/tmp/init_recovery.ora';
Enter fullscreen mode Exit fullscreen mode

Quick Fix Summary 

-- Step 1: Identify the failing background process in alert log
SELECT VALUE FROM V$DIAG_INFO WHERE NAME = 'Diag Trace';

-- Step 2: Check resource usage
SELECT NAME, VALUE FROM V$PARAMETER
WHERE NAME IN ('processes','sga_target','sga_max_size','memory_target');

-- Step 3: Adjust parameters as needed and restart
ALTER SYSTEM SET SGA_TARGET = 2G SCOPE = SPFILE;
ALTER SYSTEM SET PROCESSES = 300 SCOPE = SPFILE;

SHUTDOWN IMMEDIATE;
STARTUP;
Enter fullscreen mode Exit fullscreen mode

Prevention Tips

1. Monitor resource usage proactively:

-- Run this regularly to catch resource pressure early
SELECT NAME, VALUE AS MAX_VALUE,
       (SELECT COUNT(*) FROM V$PROCESS) AS CURRENT,
       ROUND((SELECT COUNT(*) FROM V$PROCESS) / VALUE * 100, 2) AS PCT_USED
FROM V$PARAMETER
WHERE NAME = 'processes';
Enter fullscreen mode Exit fullscreen mode

2. Validate kernel parameters before and after every OS or Oracle patch. Use Oracle's runInstaller prerequisite checks or the orachk utility to confirm all OS-level requirements are met. Schedule periodic planned restarts during maintenance windows to catch startup issues before an unplanned outage forces your hand.

Related Errors

Error Code Description
ORA-00444 Background process failed to start (precedes ORA-00445)
ORA-27102 Out of memory — SGA allocation failed at OS level
ORA-04031 Unable to allocate shared memory in the SGA
ORA-00821 SGA_TARGET value too small for configuration
ORA-00600 Internal error — may accompany ORA-00445 on binary corruption

📖 Want a more detailed guide?
Check out the full in-depth version (Korean) on oraerror.com — includes detailed analysis, additional SQL examples, and prevention tips.

Top comments (0)