java.lang.OutOfMemoryError: PermGen space in tomcat while loading site

Hi,
I got the following error while loading a page after deploying my app in tomcat :

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SEVERE: Servlet.service() for servlet [spring-servlet] in context with path [/flights-india-yt] threw exception [Handler processing failed; nested exception is java.lang.OutOfMemoryError: PermGen space] with root cause
java.lang.OutOfMemoryError: PermGen space
      at java.lang.ClassLoader.defineClass1(Native Method)
      at java.lang.ClassLoader.defineClassCond(Unknown Source)
      at java.lang.ClassLoader.defineClass(Unknown Source)
      at java.security.SecureClassLoader.defineClass(Unknown Source)
      at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2888)
      at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1172)
      at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
      at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1558)
      at org.drools.rule.builder.dialect.java.parser.JavaParser.<init>(JavaParser.java:11641)
      at org.drools.rule.builder.dialect.java.parser.JavaParser.<init>(JavaParser.java:219)
      at org.drools.rule.builder.dialect.java.JavaExprAnalyzer.analyzeBlock(JavaExprAnalyzer.java:90)
      at org.drools.rule.builder.dialect.java.JavaDialect.analyzeBlock(JavaDialect.java:258)
      at org.drools.rule.builder.dialect.java.JavaConsequenceBuilder.build(JavaConsequenceBuilder.java:91)
      at org.drools.rule.builder.RuleBuilder.build(RuleBuilder.java:99)
      at org.drools.compiler.PackageBuilder.addRule(PackageBuilder.java:1813)
      at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:745)
      at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:338)
      at com.yatra.platform.rules.BusinessRulesExecutor.getNewRuleBase(BusinessRulesExecutor.java:140)
      at com.yatra.platform.rules.BusinessRulesExecutor.getRuleBase(BusinessRulesExecutor.java:108)
      at com.yatra.platform.rules.BusinessRulesExecutor.fireBusinessRules(BusinessRulesExecutor.java:153)
      at com.yatra.platform.rules.BusinessRulesExecutor.fireBusinessRules(BusinessRulesExecutor.java:73)
      at com.yatra.platform.rules.BusinessRulesExecutor.fireBusinessRules(BusinessRulesExecutor.java:102)
      at com.yatra.products.air.web.controller.HomePageController.processHomeRules(HomePageController.java:66)
      at com.yatra.products.air.web.controller.HomePageController.home(HomePageController.java:58)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
      at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
      at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)

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How should i interpret it and resolve it
Thanks