Hi,   I did restart nifi , but the problem still persists.   The next release of nifi will add a new DBCP connection Pool: Hadoop DBCP connection pool: https://issues.apache.org/jira/browse/NIFI-7257 It will, hopefully, solve the issue.   For my part, I implemented a specific connector which modifies the classpath: https://github.com/dams666/nifi-dbcp-connectionpool   In short:   public static final PropertyDescriptor DB_DRIVER_LOCATION = new PropertyDescriptor.Builder() .name("database-driver-locations") .displayName("Database Driver Location(s)") .description("Comma-separated list of files/folders and/or URLs containing the driver JAR and its dependencies (if any). For example '/var/tmp/mariadb-java-client-1.1.7.jar'") .defaultValue(null) .required(false) .addValidator(StandardValidators.createListValidator(true, true, StandardValidators.createURLorFileValidator())) .expressionLanguageSupported(ExpressionLanguageScope.VARIABLE_REGISTRY) .dynamicallyModifiesClasspath(true) .build(); ... dataSource = new BasicDataSource(); dataSource.setDriverClassName(drv); dataSource.setDriverClassLoader(this.getClass().getClassLoader());   But I still got same error message:   PutSQL[id=94d192a9-fd1d-3c59-99be-d848f8902968] Failed to process session due to java.sql.SQLException: Cannot create PoolableConnectionFactory (ERROR 103 (08004): Unable to establish connection.): org.apache.nifi.processor.exception.ProcessException: java.sql.SQLException: Cannot create PoolableConnectionFactory (ERROR 103 (08004): Unable to establish connection.)   My setup:   Database Connection URL : jdbc:phoenix:zk4-xxx.ax.internal.cloudapp.net,zk5-xxx.ax.internal.cloudapp.net,zk6-xxx.ax.internal.cloudapp.net:2181:/hbase-unsecure   Database Driver Class Name: org.apache.phoenix.jdbc.PhoenixDriver   Damien ... View more