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|
Limitations of ASM for RAC Database Use
Oracle RAC
Cluster Tips by Burleson Consulting |
This is an excerpt from the bestselling book
Oracle Grid & Real Application Clusters. To get immediate
access to the code depot of working RAC scripts, buy it
directly from the publisher and save more than 30%.
No ASM Support for:
* External Tables (yet 10g
offers much improved External Table Support)
* Transportable Tablespaces
capability is somewhat restrictive. It can be used with RMAN only.
* Reports, Export/Import
output cannot go onto ASM resources.
* SQL*Loader Files can not be
located in ASM
* Oracle Home Files – Oracle
need either local file system or fully functional cluster file
system
Supported File Types
The following table shows the
types of files ASM Supports. The default template specifications
assign fixed attributes like level of redundancy and level of
striping.
|
FILE TYPE |
SUPPORTED BY
ORACLE ASM |
DEFAULT TEMPLATE |
|
Control Files |
Yes |
CONTROLFILE |
|
Data Files |
Yes |
DATAFILE |
|
Redo Log Files |
Yes |
ONLINELOG |
|
Archived Log Files |
Yes |
ARCHIVELOG |
|
Trace Files |
No |
-- |
|
Database Temporary Files |
Yes |
TEMPFILE |
|
Data File Backup pieces |
Yes |
BACKUPSET |
|
Archive Log Backup Pieces |
Yes |
BACKUPSET |
|
Parameter Files |
Yes |
PARAMTERFILE |
|
Operating System Files |
No |
-- |
|
Alter Log Files |
No |
-- |
|
Flashback Logs |
Yes |
FLASHBACK |
|
Data Punp Sets |
Yes |
DUMPSET |
Table 5.4: The types of files
ASM Supports
ASMLib
For the Linux platform, Oracle
provides ASMLib which is a library add-on for the ASM. ASMLib is the
kernel driver for generic Linux implementation. ASMLib allows an
Oracle Database using ASM more efficient and capable access to the
disk groups it is using.
At the time of the writing of
this chapter, the Oracle ASMLib 1.0.0 was available for free
download at
http://otn.oracle.com/tech/linux/asmlib/index.html. This library
is available for the following Linux flavors.
* Red Hat Advanced Server 2.1
(x86)
* Red Hat Enterprise Linux 3 AS
* United Linux 1.0 SP3 / SLES 8
SP3 (x86)
* United Linux 1.0 SP3 / SLES 8
SP3 (ia64)
* United Linux 1.0 SP3 / SLES 8
SP3 (amd64)
The ASM Library Files are
available as rpm(s). Install the packages by using the following
command:
rpm -Uvh
oracleasm-support-1.0.0-1.i386.rpm \
oracleasm-lib-1.0.0-1.i386.rpm \
oracleasm-2.4.9-e-enterprise-1.0.0-1.i686.rpm
Once the ASMLib software is
installed, the ASM driver needs to be loaded, and the driver
filesystem needs to be mounted. This is achieved by the
initialization script, /etc/init.d/oracleasm.
By root privilege, execute the
/etc/init.d/oracleasm script with the configure option. It will ask
for the user and group that default to owning the ASM driver access
point. If the database was running as the oracle user and the dba
group, the output would look like this:
[root@ca-test1 /]# /etc/init.d/oracleasm configure
Configuration of CFS or Raw
Devices
In the previous sections, the
creation and usage of the ASM instance resources was examined. In
this section, how to configure raw devices and Cluster File Systems
will be covered. For studying the creation of raw partitions, a
typical Linux environment and raw device configuration will be used.
For CFS, three products will be examined; PolyServe Matrix Server;
OCFS; and Veritas CFS
Once the decision has been made
to use either raw devices or cluster file system files, a plan needs
to be made for setting up the necessary storage volumes and file
systems. The RAC system requires a minimum set of files/raw devices
for creating default tablespaces and setting the redo log files etc.
If the DBCA utility will be used
to create the initial database, there are certain requirements that
need to be met concerning the default schemas. Raw devices need to
be provided or file systems to store them. Then the user-defined or
business application-related schemas and tablespaces are created.
In the case of UNIX and
Linux-oriented cluster platforms, most of the vendors provide some
kind of volume manager or tool, which helps to create volumes of
manageable size and layout at the host level. These volumes can be
used by the RAC database as raw partitions. Optionally, when using
the cluster file system, the file system can be made and mounted.
When planning to use the volumes as the raw partitions, it may be
necessary to plan and pre-create a large number of partitions with
appropriate sizes. Figure 5.14 shows the relationship between the
storage volumes and how they are presented for the use of the RAC
database.
A LUN is the concept of the
usable disk. LUN stands for Logical Unit Number. It is a physical
disk, as seen by the node or host. They are also called RAID logical
drives. Once they are introduced into a disk group at the volume
manager level, they become the basis for logical volume creation.
Volumes are usable pieces carved out of the storage pool. When they
are used by the database application, they are the raw partitions.
When a file system is created on the volumes, they become mountable
at the operating system level. Figure 5.14 shows the connection
between the storage structures.
Figure 5.14: Storage
Volume Relations
In the case of a Windows
platform, the Windows disk manager provides a facility to create raw
partitions. When using the OCFS (Oracle Cluster File System) module,
Veritas CFS or PolyServe, appropriate cluster file system mount
points can be created.
