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ORA-24327: need explicit attach before authenticating a user (DBD ERROR: OCISessionBegin)

One of the OEM agent log has the following error, and some of the jobs fail due to the database connection issues:

$ grep ORA-24327 *
gcagent.log.16:em_error=Could not connect to dbsnmp/(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=racnode1.virtuallab)(Port=1521))(CONNECT_DATA=(SID=RACTESTDB1))): ORA-24327: need explicit attach before authenticating a user (DBD ERROR: OCISessionBegin)

The output from CA( Corrective Action) job:

Connector descriptor is (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=racnode1.virtuallab)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=RACTESTDB)(SERVER=DEDICATED)))
Could not connect to SYSTEM/(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=racnode1.virtuallab)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=RACTESTDB)(SERVER=DEDICATED))):ORA-24327: need explicit attach before authenticating a user (DBD ERROR: OCISessionBegin)

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Find Oracle SQL Execution History Details

DBAs are always asked about the database performance issues, which are mostly caused by some SQL queries’ execution plan changes.

This post demonstrates how to get a SQL query performance details like executions, disk/physical read/write, cpu time, elapsed time and waiting time, etc.

With the help of those statistics of a specific SQL query, DBA can easily identify the issue, and remediate it by applying SQL plan baselines.

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What to Check Before Truncate a Table?

This post shows what need to be checked before truncating a table in Oracle. Otherwise it might cause unexpected tables’ data loss and application outage in mission critical environment.

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How to Configure SQL Developer to Connect to PostgreSQL

A client likes to use Oracle SQL Developer to connect to PostgreSQL databases. During the configuring, some errors occurred. This post shows how to resolve the configuration issues from Oracle SQL Developer and third party libraries .

The typical issue is you will get the following errors when connecting to PostgreSQL database by using non ‘postgres’ users.

Failure -FATAL: database "user1" does not exist

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So it is not correct that we have to use ‘postgres’ username which is the same name as database name to connect to PostgreSQL databases. Instead, any user can be used to connect to a PostgreSQL database.

How to Create Service on Non-RAC PDB

As we know, we can use ‘srvctl’ utility to create a service for a RAC database. Now I demonstrate how to create a service for a standalone CDB/PDB database.

For non CDB/PDB database, we can use ‘service_name’ parameter to specify service names.

SQL> show parameter service_name;

 NAME             TYPE    VALUE
 --------------- ------- ------------------
 service_names   string  HR,STOCK,INVENTORY

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