Installation guide

71775 32434 45% 0.05K 957 75 3828K buffer_head

19460 15050 77% 0.27K 1390 14 5560K radix_tree_node

13090 13015 99% 0.03K 110 119 440K avtab_node

12495 11956 95% 0.03K 105 119 420K size-32

...

Slab caches are a special memory pool in the kernel for adding and removing objects (e.g., data structures or

data buffers) of the same size. It is a cache for commonly used objects where the kernel does not have to re-allo-

cate and initialize the object each time it is being reused, and subsequently free the object each time it is being

destroyed. The slab allocator scheme basically prevents memory fragmentation and it prevents the kernel from

spending too much time allocating, initializing, and freeing the same objects.

The kernel parameter /proc/sys/fs/aio-max-nr limits the number of concurrent asynchronous I/O re-

quests. The default value 65536 (64K) may be too low for Oracle database servers. You can monitor the cur-

rent number of the concurrent I/O requests represented in /proc/sys/fs/aio-nr and increase the above

limit if necessary. For example,

# cat /proc/sys/fs/aio-nr

65536

# echo 3145728 > /proc/sys/fs/aio-max-nr

The recommended value for Oracle validated configurations is 3145728.

Storage Configuration for Oracle 10g RAC and Standalone Server

Red Hat Enterprise Linux provides variety of options for storage management. Red Hat Enterprise Linux 5 sup-

ports dynamic device configuration and re-configuration, native multipathing, logical volume manager, GFS

cluster file system (can also be used in the standalone mode), ext3, NFS file systems, and iSCSI initiator. n ad-

dition, Oracle provides OCFS2 file system and Automatic Storage Management (ASM) for Oracle database

files.

Oracle database storage management provides the following choices for placing database files:

1. Traditional file systems – standalone and cluster-aware

2. Standard UNIX raw devices

3. ASM

● on raw devices

● on block devices with ASMLib

● on block devices without ASMLib

Raw devices are deprecated in Red Hat Enterprise Linux 5. The implementation of raw devices in Linux is just

a wrapper that opens underlying block devices with O_DIRECT flag for direct I/O. The raw devices do not

give any performance benefits to Oracle database server. They are required only for Oracle 10g R2 RAC with

Clusterware 10.2.0. We will not consider raw device configuration for any other purposes.

Oracle 10g R2 is certified on Red Hat Enterprise Linux 5 with ext3, GFS, OCFS2, and ASM storage options in