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In the last two days, Oracle 12.2 has been installed on the virtual machine, and the installation process is quite smooth. However, the database cannot be connected after the virtual machine is restarted. Execute sqlplus / as sysdba to report an error ORA-12547: TNS:lost contact

Why? After the installation, the tests are all good, how can this happen after rebooting? There are many ways to deal with it on the Internet:

The solutions given on the Internet are as follows:

1. Check whether the operating system kernel parameters are correct [oracle@rhel7 database] $ulimit-acore file size (blocks,-c) 0data seg size (kbytes,-d) unlimitedscheduling priority (- e) 0file size (blocks,-f) unlimitedpending signals (- I) 15738max locked memory (kbytes,-l) 64max memory size (kbytes) -m) unlimitedopen files (- n) 1024pipe size (512 bytes,-p) 8POSIX message queues (bytes,-Q) 819200real-time priority (- r) 0stack size (kbytes,-s) 10240cpu time (seconds,-t) unlimitedmax user processes (- u) 2047virtual memory (kbytes -v) unlimitedfile locks (- x) unlimited 2, confirm whether there is a problem with the permissions of the $ORACLE_HOME/bin/oracle file (you need to view the $ORACLE_HOME/bin/oracle and $GRID_HOME/bin/oracle files under rac) The correct permission is: [oracle@normal adump] $ll $ORACLE_HOME/bin/oracle-rwsr-s--x 1 oracle oinstall 232399083 Aug 28 17:23 / u01/app/oracle/product/11.2.0/db_1/bin/oracle if the permission is not for chmod 6751 $ORACLE_HOME/bin/oracle 3, check the environment variable echo $ORACLE_HOME echo $ORACLE_SID echo $LD_LIBRARY_PATH-- Note: different operating systems this environment variable will be different echo $PATH 4, Check whether the file size of $ORACLE_HOME/bin/oracle and $ORACLE_HOME/rdbms/lib/config.o is 0 If the size is 0, you need to recompile the oracle software: [oracle@normal backup] $relink all writing relink log to: / u01/app/oracle/product/11.2.0/db_1/install/relink.log 5, and use the operating system trace command to track the sqlplus connection process to observe the trace file. Ltrace-f-o / tmp/sqlplus.log sqlplus / as sysdba or truss command

Reference from: http://blog.csdn.net/ch7543658/article/details/38901355

Follow all the five steps above or keep reporting an error.

Finally, I carefully check the kernel configuration and the limit parameter configuration of oracle users. It is found that one parameter configuration in limits.conf is too small. What I configured is:

Oracle hard stack 1024

The official document suggests 10240.

Then I remembered that when installing Oracle, I was lazy and did not configure kernel parameters and limits.conf files. Instead, I used fix.sh script to modify it. After modification, I found that some configurations were not written in the configuration file, so I wrote the missing configuration manually, and made a mistake, which eventually led to the above error.

After modifying the limits.conf file, log in with the oracle user again and no longer report an error.

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