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Don Burleson Blog 







  Connecting to a hung database with the -prelim option

Oracle Database Tips by Donald BurlesonMarch 29, 2015

Question:  My Oracle instance is not accepting SYSDBA connections.  How do I connect to Oracle to do a shutdown abort?

Answer:  If you cannot connect, you have two choices, either wait (impacting the end users) or immediately bounce the instance. 

1 - Killing the background processes and removing the RAM segments. See killing oracle instance tips.

2 - Using the -prelim SQL*Plus option to bypass creation of a new SQL*Plus session.

Also see my notes on hung database analysis.

The -prelim option of the SQL*Plus connect string was introduced in 10g to bypasses the creation of a new session in cases where the database is hung and not accepting traditional sqlplus connections:.

$sqlplus /nolog
SQL> set _prelim on
SQL> conn / as sysdba
Prelim connection established
SQL> shutdown abort

Here is how to quickly generate a hang analysis immediately prior to re-starting a hung production instance:

/u01/app/oracle/bin>sqlplus system/mypass -prelim /nolog
SQL*Plus: Release - Production  

SQL> oradebug setmypid
Statement processed.  

SQL> oradebug hanganalyze 12
Hang Analysis in /u01/app/oracle/admin/mysid/udump/mysid_ora_1234.trc

You can also use the -prelim argument to capture Automated Session  History (ASH) data for a hung database:

/u01/app/oracle/bin>sqlplus system/mypass -prelim /nolog
SQL*Plus: Release - Production  

SQL> oradebug setmypid
Statement processed.  

SQL> oradebug dump ashdump 10
Statement processed.  

>alter session set events 'immediate trace name ashdump level 10';

$sqlplus -prelim /nolog

SQL> connect / as sysdba
Prelim connection established

SQL> oradebug setmypid
Statement processed.

SQL> oradebug hanganalyze 12

Hang Analysis in C:\oracle\admin\orcl\udump\orcl_ora_5564.trc

SQL> oradebug dump systemstate 10

Statement processed.

SQL> oradebug tracefile_name C:\oracle\admin\orcl\udump\orcl_ora_5598.trc


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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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