On linux/unix platform, how does one check which databases or instances exist on the OS?

On the linux/unix platform, it is not difficult to check which databases or instances exist on the OS. As some colleagues asked this question, I wrote down the method, someone may ask, but maybe another person may not. I hope it will help some friends who are not or just new. On the linux/unix platform, you can view the number of databases on the OS. There are three query methods: 1. You can run the lsnrctl status Command to view the number of databases on the OS, you can view the database instances that have been registered to listener. To a certain extent, it indicates that there are database instances listed in the command results on the OS. Of course, commands except unstarted and unregistered include: # su-oracle $ lsnrctl status [oracle @ oraclelinux ~] $ Lsnrctl status LSNRCTL for Linux: Version 11.2.0.3.0-Production on 04-AUG-2013 06: 03: 29 Copyright (c) 1991,201 1, Oracle. all rights reserved. connecting to (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.171.100) (PORT = 1521) STATUS of the LISTENER ---------------------- Alias LISTENERVersion TNSLSNR for Linux: version 11.2.0.3.0-ProductionStart Date 04-AUG-2013 05: 57: 12 Uptime 0 days 0 hr. 6 Min. 17 secTrace Level offSecurity ON: Local OS AuthenticationSNMP OFFListener Parameter File/dba/oracle/product/11.2.0/db_1/network/admin/listener. oraListener Log File/dba/oracle/diag/tnslsnr/oraclelinux/listener/alert/log. xmlListening Endpoints Summary... (DESCRIPTION = (ADDRESS = (PROTOCOL = tcp) (HOST = 192.168.171.100) (PORT = 1521) (DESCRIPTION = (ADDRESS = (PROTOCOL = ipc) (KEY = EXTPROC1521) Services Summ Ary... service "litest" has 1 instance (s ). instance "litest", status READY, has 1 handler (s) for this service... service "litestXDB" has 1 instance (s ). instance "litest", status READY, has 1 handler (s) for this service... the command completed successfully from The result set in The above table, we can see that there is a "litest" database instance registered to listener, it indicates that at least one database instance named litest exists on the operating system. 2. when viewing the database or instance through cat/etc/oratab, A line of records will be added to the/etc/oratab file, even if the database instance is not started, You can also view this method. Command: # cat/etc/oratab [root @ oraclelinux ~] # Cat/etc/oratab # This file is used by ORACLE utilities. it is created by root. sh # and updated by either Database Configuration Assistant while creating # a database or ASM Configuration Assistant while creating ASM instance. # A colon, ':', is used as the field terminator. A new line terminates # the entry. lines beginning with a pound sign, '#', are comments. # Entries are of the form: # $ ORACLE_SID: $ ORACLE_HOME: <N | Y >:## The first and second fields are the system identifier and home # directory of the database respectively. the third filed indicates # to the dbstart utility that the database shocould, "Y", or shocould not, # "N", be brought up at system boot time. # Multiple entries with the same $ ORACLE_SID are not allowed. # litest:/dba/oracle/product/11.2.0/db_1: N from the result of the last row in the table above, we can see that there is an OS named lites T database (including instances) 3. View through ps-ef | grep ora_pmon. If the database or instance has been started in nomount mode, a pmon process will be generated, therefore, we can check whether the OS has a pmon process to check whether several database instances exist. Each instance has a pmon process. If multiple pmon processes exist, this means that there are multiple database instance commands on the OS: # ps-ef | grep pmon [root @ oraclelinux ~] # Ps-ef | grep pmonoracle 3491 1 0 06:10? 00:00:00 ora_pmon_litestroot 3528 3459 0 00:00:00 pts/1 grep pmon from the results in the above table, we can see that a database instance named "litest" is running on the OS