Zheng Tech Blog

Now JDK 7 has been out for a while (JDK 8 is out too as of writing). There are some caveats using WebLogic Server with JDK 7 you might want to know, not matter it's on 10.3.6 or 12c. 1. Out of memory error on starting Admin Server. This error is caused by the fact that the new JVM requires more PermGen space. Depending on your RAM, you can set it >350m. In my case, I would set the perm size to 512M. -XX:MaxPermSize=512m 2. In some cases, the new compiler generates larger byte code. It is possible that a large method may exceed the 64KB limit per method. In this situation, you may need to refactor the method. This seems to only affect WebLogic 10.3.6 3. Classes may have been removed that are from the internal package sun.*, or that have been marked as deprecated in a previous version of the JVM. If an application uses these removed methods, a ClassNotFound exception will occur. 4. JDBC 4.1 is introduced in JDK7. JDBC 4.1 methods are not currently supported in ...

Although there is a similar blog entry on this topic, I’d rather to blog it anyway for my own reference. If the WebLogic Server was installed on Linux and when starting, you might see the following message: What happened is the default JRockit JVM prefers to uses large pages for Java heap but the Linux OS is not setup yet for this option. HugePages is a feature integrated into the Linux kernel 2.6. It’s a method to have larger page size that is useful for working with large memory. HugePages is userful for both 32-bit and 64-bit configurations. Its size varies from 2MB to 256MB, depending on the kernel version and the hardware architecture. Using HugePages reduces the OS maintenance of page states, and increases Translation Lookaside Buffer (TLB) hit ratio. Run the following will show a filesystem of type hugetlbfs configured in the kernel: cat /proc/filesystems First, we need to create the hugepages director...