As Published In July/August 2004

Linux Improvements in Oracle 10g
By David A. Kelly

Very large memory support. Oracle9i included an option called VLM—very large memory—that allows Oracle, on a 32-bit machine, to create, through the use of a shared file system, a database and memory space that's larger than what 32-bit systems can address in one address space. In deployment, however, it turned out that using this in certain circumstances could result in fragmentation in the kernel memory, because of the way certain areas were mapped. The result was that there was a limit on the number of processes that could attach.

By working with Red Hat and SuSE, Oracle was able to propose an API called Remap File Pages that's now in Red Hat Enterprise Linux 3 and will be part of SuSE Linux Enterprise Server 9. Remap File Pages avoids memory fragmentation and avoids using up low memory so that organizations can have more, faster connections and increased stability. "Although that's available as a patch for Oracle9i, it comes out of the box with Oracle 10g," says Wim Coekaerts, director of Linux Engineering at Oracle. "So now, by default, when you turn on VLM support, it will automatically start using Remap File Pages capabilities."

Direct I/O support. Previously, the database supported only direct I/O for the Oracle Cluster File System (OCFS). Now, with Oracle 10g, Network File System (NFS) also supports direct I/O in the file system. "With Oracle 10g, you have direct support, directly in the database, without having to apply a patch," says Coekaerts. "That can really improve performance—especially for NFS, where it speeds everything up. It's really good for running RAC on NFS." According to Coekaerts, it can even be valuable on a single node, because you don't have to end up caching data in the OS file system cache but can instead use Oracle's algorithm for it.

Streamlined installation. "In Oracle 10g, the installation of the database is just one CD, so within five minutes or so, you can be up and running—it's really, really nice," says Coekaerts. The streamlined installer has also been updated for the new versions of Linux, such as Red Hat Enterprise Linux 3 or SuSE service pack 3, so that administrators don't have to apply any OS-specific patches.

ASM. Oracle 10g supports a new feature called Automatic Storage Management (ASM), which allows Oracle to manage the entire storage pool of raw devices. "We've added a Linux module that enhances the new ASM function," comments Coekaerts. "We have a driver that scans the available disks and provides them automatically to Oracle, making management even easier. It's available on OTN, so that customers running Oracle 10g can use that kernel module and just tag the disks that are ASM volumes. Then, when Oracle starts up, it just makes a call to the kernel module and grabs all the disks, creates a special device, and gives that to Oracle, which will use it to do I/O. It's very similar to async I/O, but it gives us a chance to do some automatic probing of the disks and optimize the I/O path."

OCFS. Although OCFS version 1.0 works just as well with Oracle 10g as it did with Oracle9i, OCFS version 2 on Linux can manage both the Oracle database and the Oracle code itself. For example, on a four-node cluster, an administrator will have to do only one install of Oracle 10g, and the installer will understand the cluster file system and will load it into the right places, making deployment and updates much easier. "Imagine you have an eight-node cluster. Prior to OCFS version 2, you'd have to install Oracle eight times and then apply any patches eight times. Instead, with OCFS having a single, shared home, you can install it just once and apply the patches once, from one file system—so it makes management a lot easier," explains Coekaerts.