How To Check if Oracle Gateway for MSSQL is Installed:
If the following command returns a list of files, then Oracle Gateway for MSSQL is installed:
# ls -l $ORACLE_HOME/dg4msql
If Oracle Gateway for MSSQL is installed, the following command will show you the Oracle Gateway version details:
# $ORACLE_HOME/bin/dg4msql
To check if Oracle Gateway is configured on the system, search for "dg4msql" in the listener status output: [Provide the listener name if you are using a non-default listener name]
# lsnrctl status
Reference:
https://docs.oracle.com/database/121/OTGIS/configsql.htm#OTGIS900