Compaq ProLiant 1850R Modifying Physical Cluster Resources in a Compaq Paralle - Page 4

Modifying Physical Cluster Resources in a Compaq Parallel Database Cluster 4 • When an existing array is removed from the cluster's shared storage, if the array was not the last one brought online, the order of the drives will change for all cluster nodes. Preventing the Issue It is highly recommended that a power-on sequence for the shared storage arrays be determined during the initial configuration of the cluster. Thereafter, this power-on sequence must be followed exactly to ensure that each node sees the disk in a proper order in the Windows NT Disk Administrator utility. When adding shared storage (a physical drive or an array), make it the last drive (or array) to be brought online. In the case of adding an array, make sure it is the last array to be powered-on; and add it to the power-on sequence as such. On each node use disk administrator to verify that the disks are brought on-line in the expected order before starting the Oracle instance. Also, verify that the PGMS service is set to start manually. Simplifying Detection of the Issue A method that simplifies detection of the issue is to create logical partitions that are not all the same size. With different-sized logical partitions, disk administrator can be used to see the size of the partitions, which can be quickly and easily compared against the sizes written in the suggested Oracle worksheet. If the drive order in the worksheet does not compare with the drive order shown in disk administrator, the drives were brought online out of sequence. For example, the shared disks associated with the database could have a small unused partition as the first partition on the disk. Assuming there are three disks associated with the database, a sample configuration might be: • Harddisk1 Partition1 is sized to 11 MB • Harddisk2 Partition1 is sized to 12 MB • Harddisk3 Partition1 is sized to 13 MB When the cluster is powered on, if disk administrator shows harddisk1, partition1 as 12MB or 13MB, the drives were brought on-line out of sequence. The cluster should be shut down and restarted correctly. What Oracle Component is Affected? How does the drive ordering issue manifest itself in Oracle8 Server? The focal point of this issue resides in the Oracle symbolic link table files; frequently identified as ORALINKx.TBL. These files create symbolic links, which are used by Oracle8 Server to map specific Oracle database files to specific hard drive partitions. A link is required for each database file. A two node cluster requires nine database files and one cluster file, and therefore requires ten links. The first symbolic link table file is used by a two-node cluster. Each additional node requires two more database files, two more links, and one more symbolic link table file . Oracle suggests using a worksheet to define the symbolic links. For more information about the worksheet, refer to the Oracle Parallel Server Getting Started Release 8.0.5 for Windows NT manual. An example of such a worksheet follows. The example assumes the cluster consists of two nodes - Node1 has two internal disk drives and Node2 has one internal disk drive. Additionally, it assumes the shared storage consists of two fibre channel arrays - the first array has three RAID logical drives and the second array has two RAID logical drives. Therefore, ECG001/1298