Release Notes

15 Migrating an Oracle Database to Dell EMC SC Series Storage | CML1001

3.5 Configure Oracle disk groups

This section describes some common practices when creating disk groups on an SC Series array.

3.5.1 Automatic Storage Management (ASM)

Oracle ASM is the preferred storage management system since Oracle version 11. It provides three levels of

storage redundancy which allows data to be mirrored through its software. ASM distributes data files across

all disks in an ASM disk group to maximize performance and can dynamically restripe data files when

additional disks are added. In general, it is not necessary to mirror the data on the OS or inside ASM because

the Data Protection is already provided by the SC Series array natively. Therefore, in most Oracle

environments, it is recommended to use External Redundancy for ASM disk groups which reduces overall

IOPS and results in better I/O performance. Additional guidelines include:

• Separate diskgroups should be used for data and archivelogs.

• A database can span across multiple diskgroups.

• At least two volumes should be configured in each diskgroup.

• All volumes in the same diskgroup should have the same capacity and performance attributes.

• Diskgroups should be mounted and used by a database exclusively and not shared with other

databases if possible. This simplifies using array-based snapshots for backup and recovery.

For more information on Oracle best practices with SC Series storage, see Dell SC Series Storage

with Oracle ASM Best Practices.

3.5.2 Linux Logical Volume Manager (LVM)

Similar to ASM, it is not necessary to mirror logical volumes in LVM. LVM allows striping data files across

multiple volumes in a volume group. Unlike ASM, the striping needs to be configured by administrators

explicitly, and automatic restriping is not available when extending a volume group in LVM.

3.5.3 Oracle data files

Oracle ASM works with SC Series volume thin provisioning by enabling the data file auto extensible feature.

This allows the data files to start with a small size and to grow incrementally as data is written to the data files.

3.6 Understanding endian formats

Endianness refers to the format of how bytes of numeric values are ordered within memory. It is an important

determining factor in the ability to migrate a database or transport tablespaces across platforms. There are

several endian formats: little-, big-, or mixed-endian (middle-endian). Of the three formats, mixed-endian is

rare and does not appear in the Oracle list of supported endian types for platform migrations. See section

3.6.2.

With little-endian, a numeric value is written or stored in memory with the smallest part (byte), or least

significant part (byte), of the value first, followed by more significant parts (bytes) in successive order. In

contrast, with big-endian, a numeric value is written or stored in memory with the most significant part (byte)

first, followed by lesser significant parts (bytes). For example, given the value 4321

(10D7

), and 8-bit

memory words, the value would be stored as follows: