Oracle Database Express Edition (XE)

Hello,

Oracle XE: -->SQL*Plus: Release 11.2.0.2.0 Production
My Operating System:--> CentOS Linux release 7.5.1804 (Core)

I was receiving error in one of Java file this error:

java.sql.SQLException: Listener refused the connection with the following error:
ORA-12519, TNS:no appropriate service handler found
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:489)
at oracle.jdbc.driver.PhysicalConnection.(PhysicalConnection.java:553)
at oracle.jdbc.driver.T4CConnection.(T4CConnection.java:254)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:528)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at DB.getOracleConnection(DB.java:13)
at Advertisement.displayBanners(Advertisement.java:85)
at SiteTemplate.leftbar(SiteTemplate.java:334)
at SiteTemplate.siteHeader(SiteTemplate.java:383)
at DisplayNews.doGet(DisplayNews.java:22)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:486)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: oracle.net.ns.NetException: Listener refused the connection with the followin error:

I google and found some suggestions to correct sga_target and check session. I used the following commands:

ALTER SYSTEM SET sga_target=1g SCOPE=SPFILE;
SHUTDOWN IMMEDIATE;
STARTUP;

From here my bad started and was not able to start database. The error was:

ORA-00838: Specified value of MEMORY_TARGET is too small, needs to be at least 4108M

I found this and tried to apply

Now I am receiving this and stuck as well as not able to start database

SQL> startup pfile=/tmp/pfile.bac
ORA-47500: XE edition memory parameter invalid or not specified
ORA-01078: failure in processing system parameters

Please advise as to why its not working even I am specifying 4108M in pfile.bac?

Best regards