用tomcat发布的网站时常出现连接数据库被拒绝的错误！

最近部署在tomcat上的网站在打开时总是出现连接错误，重启tomcat后又正常了，因为总是出现这个问题，找不到原因请大神们赐教！
错误提示如下：
HTTP Status 500 - javax.servlet.ServletException: java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(TMP=)(VSNNUM=186646784)(ERR=12518)(ERROR_STACK=(ERROR=(CODE=12518)(EMFI=4))(ERROR=(CODE=12560)(EMFI=4))))

type Exception report

message javax.servlet.ServletException: java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(TMP=)(VSNNUM=186646784)(ERR=12518)(ERROR_STACK=(ERROR=(CODE=12518)(EMFI=4))(ERROR=(CODE=12560)(EMFI=4))))

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: javax.servlet.ServletException: java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(TMP=)(VSNNUM=186646784)(ERR=12518)(ERROR_STACK=(ERROR=(CODE=12518)(EMFI=4))(ERROR=(CODE=12560)(EMFI=4))))
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

javax.servlet.ServletException: java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(TMP=)(VSNNUM=186646784)(ERR=12518)(ERROR_STACK=(ERROR=(CODE=12518)(EMFI=4))(ERROR=(CODE=12560)(EMFI=4))))
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:916)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:845)
org.apache.jsp.index_jsp._jspService(index_jsp.java:595)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(TMP=)(VSNNUM=186646784)(ERR=12518)(ERROR_STACK=(ERROR=(CODE=12518)(EMFI=4))(ERROR=(CODE=12560)(EMFI=4))))
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:179)
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:333)
oracle.jdbc.driver.OracleConnection.(OracleConnection.java:404)
oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.java:468)
oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:314)
java.sql.DriverManager.getConnection(Unknown Source)
java.sql.DriverManager.getConnection(Unknown Source)
org.apache.jsp.index_jsp._jspService(index_jsp.java:89)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.59 logs.

Apache Tomcat/7.0.59