Linux: ORA-12518: TNS:listener Could Not Hand Off Client Connection

(Doc ID 2298954.1)

Last updated on SEPTEMBER 04, 2017

Applies to:

Oracle Net Services - Version 11.2.0.4 and later
Information in this document applies to any platform.

Symptoms

On : 11.2.0.4 version, Clusterware

When attempting to connect to database via listener,
the following error occurs.

ERROR
-----------------------

ERROR:
ORA-12518: TNS:listener could not hand off client connection


15-AUG-2017 01:40:01 * (CONNECT_DATA=(CID=(PROGRAM=myapp)(HOST=__jdbc__)(USER=admin))(SERVER=DEDICATED)(SERVICE_NAME=oracle)) * (ADDRESS=(PROTOCOL=tcp)(HOST=11.22.33.44)(PORT=1521)) * establish * oracle * 12518
TNS-12518: TNS:listener could not hand off client connection
 TNS-12536: TNS:operation would block
  TNS-12560: TNS:protocol adapter error
  TNS-00506: Operation would block
  Linux Error: 11: Resource temporarily unavailable

STEPS
-----------------------
The issue can be reproduced at will with the following steps:
1. sqlplus user/password@11.22.33.44:1521/oracle

BUSINESS IMPACT
-----------------------
The issue has the following business impact:
Due to this issue, users cannot connect to DB successfully.

Cause

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