Listing Databases on an Oracle DB node

 In this blog post I am sharing a script that I wrote that will give you the list of databases running on a DB node.  The information  provided by the script is

• DB_UNIQUE_NAME
• ORACLE_SID
• DB_HOME

WHY

I have been working on a script to automatically configure OKV for all of the Oracle Databases running on a DB host.  In order to install OKV in a RAC cluster, I want to ensure the unique OKV software files are in the same location on every host when I set the WALLET_ROOT variable for my database.  The optimal location is to put the software under $ORACLE_BASE/admin/${DB_NAME} which should exist on single instance nodes, and RAC nodes.

Easy right?

I thought it would be easy to determine the name of all of the databases on a host so that I could make sure the install goes into $ORACLE_BASE/admin/{DB_NAME}/okv directory on each DB node.

The first item I realized is that the directory structure under $ORACLE_BASE/admin is actually the DB_UNIQUE_NAME rather than DB_NAME. This allows for 2 different instances of the same DB_NAME (primary and standby) to be running on the same DB node without any conflicts. 

Along with determining the DB_UNIQUE_NAME, I wanted to take the following items into account

• A RAC environment with, or without srvctl properly configured
• A non-RAC environment 
• Exclude directories that are under $ORACLE_BASE/admin that are not a DB_UNQUE_NAME running on the host.
• Don't match on ORACLE_SID.  The ORACLE_SID name on a DB node can be completely different from the DB_UNIQUE_NAME.

Answer:

After searching around Google and not finding a good answer I checked with my colleagues.  Still no good answer.. There were just suggestions like "srvctl config", which would only work on a RAC node where all databases are properly registered.  

The way I decided to this was to 

• Identify the possible DB_UNIQUE_NAME entries by looking in $ORACLE_BASE/admin
• Match the possible DB_UNIQUE_NAME with ORACLE_SIDs by looking in $ORACLE_BASE/diag/rdbms/${DB_UNIQUE_NAME} to find the ORACLE_SID name.  I would only include DB_UNIQUE_NAMEs that exist in this directory structure and have a subdirectory.
• Find the possible ORACLE_HOME by matching the ORACLE_SID to the /etc/oratab.  If there is no entry in /etc/oratab still include it.

Script:

Below is the script I came up with, and it displays a report of the database on the host.  This can be changed to store the output in a temporary file and read it into a script that loops through the databases.

#################################################################### ## Make sure that $ORACLE_BASE is set and exists before continuing #################################################################### if [ -z ${ORACLE_BASE+x} ] then echo "\$ORACLE_BASE must be set" exit 0 fi #################################################################### ## Make sure that $ORACLE_BASE/admin exists before continuing #################################################################### if [ -d ${ORACLE_BASE}/admin ] then echo "\$ORACLE_BASE is set to : ${ORACLE_BASE}" else echo "\$ORACLE_BASE is set to ${ORACLE_BASE} but ${ORACLE_BASE}/admin does not exist" exit 0 fi ######################################################################## ## Loop through $ORACLE_BASE/admin to find the list of DB_UNIQUE_NAMEs ######################################################################### for dbdir in $ORACLE_BASE/admin/* do DB_UNIQUE_NAME=${dbdir##*/} ## echo "possible DB_UNIQUE_NAME : ${DB_UNIQUE_NAME}" ######################################################################## ## Loop through $ORACLE_BASE/diag/rdbms/${DB_UNIQUE_NAME} to validate ######################################################################### for siddir in ${ORACLE_BASE}/diag/rdbms/${DB_UNIQUE_NAME}/* do db_sid=${siddir##*/} if [ -d ${siddir} ] then echo " " echo "DB_UNIQUE_NAME : ${DB_UNIQUE_NAME}" echo "ORACLE_SID : ${db_sid}" db_home=`cat /etc/oratab | grep ${db_sid} | cut -d ':' -f 2` if [ -z "${db_home}" ] then echo "ORACLE_HOME : ****** NOT IN /etc/oratab **** Cannot determine ORACLE_HOME *****" else echo "ORACLE_HOME : ${db_home}" fi echo " " fi done done

Output:

Below is the sample output from the script.. You can see that it doesn't require the DB to exist in the /etc/oratab file.

DB_UNIQUE_NAME : cdb1db1
ORACLE_SID     : cdb1db11
ORACLE_HOME    :  ******  NOT IN /etc/oratab **** Cannot determine ORACLE_HOME *****


DB_UNIQUE_NAME : daver
ORACLE_SID     : daver1
ORACLE_HOME    : /u01/app/oracle/product/19.0.0.0/dbhome_1


DB_UNIQUE_NAME : dbsgadat
ORACLE_SID     : dbsgadat1
ORACLE_HOME    : /u01/app/oracle/product/19.0.0.0/dbhome_1


DB_UNIQUE_NAME : dbsgprd
ORACLE_SID     : dbsgprd1
ORACLE_HOME    : /u01/app/oracle/product/19.0.0.0/dbhome_1

Finally:

If you are also trying to get a list of databases that are running on a DB node I hope this helps you.