disk init

Description

Makes a physical device or file usable by Adaptive Server.

Syntax

disk init 
	name = "device_name", 
	physname = { 'physical_name' | 'cache_name'} 
	skip_alloc={true | false}, 
	[vdevno = virtual_device_number,]
	size = number_of_blocks 
	[, type = 'inmemory' ]
	[, vstart = virtual_address 
		, cntrltype = controller_number] 
		[, dsync = {true | false}]
	[, directio = {true | false}]
	[, instance = "instance_name"]

Parameters

Examples

Example 1

Does not initialize pages with zeroes:

disk init name="d2", physname="/usr/sybase/devices/d3.dat", skip_alloc="true",
size="10G"

Adaptive Server does not allocate space during disk initialization if skip_alloc is set to true.

Example 2

Initializes 10MB of a disk on a UNIX system:

disk init 
name = "user_disk", 
physname = "/dev/rxy1a", 
vdevno = 2, size = 5120 

Example 3

Initializes 10MB of a disk on a UNIX operating system file. Adaptive Server opens the device file with the dsync setting, and writes to the file are guaranteed to take place directly on the storage media:

disk init 
name = "user_file", 
physname = "/usr/u/sybase/data/userfile1.dat", 
vdevno = 2, size = 5120, dsync = true

Example 4

Creates a device named “user_disk” that uses directio to write data directly to disk:

disk init 
name = "user_disk", 
physname = "/usr/u/sybase/data/userfile1.dat", 
size = 5120, 
directio= true

Example 5

creates a device named inmemory_dev:

disk init name = inmemory_dev,
physname = 'imdb_cache',
size = '3G',
type = 'inmemory'

Usage

• When dsync is on, writes to the database device are guaranteed to take place on the physical storage media, and Adaptive Server can recover data on the device in the event of a system failure.

• When dsync is off, writes to the database device may be buffered by the UNIX file system. The UNIX file system may mark an update as being completed, even though the physical media has not yet been modified. In the event of a system failure, there is no guarantee that data updates have ever taken place on the physical media, and Adaptive Server may be unable to recover the database.

• dsync is always on for the master device file.

• The dsync value should be turned off only when databases on the device need not be recovered after a system failure. For example, you may consider turning dsync off for a device that stores only the tempdb database.

• Adaptive Server ignores the dsync setting for devices stored on raw partitions—writes to those device are guaranteed to take place on the physical storage media, regardless of the dsync setting.

• disk reinit ensures that master..sysdevices is correct if the master database has been damaged or if devices have been added since the last dump of master.

• The logical name of the in-memory device cannot be the same as the name of the cache on which a device is created.

• In-memory devices are reserved for the first in-memory database you assign to it.

• You must use the physical device name as the logical name of the in-memory device.

• The logical name of the in-memory device must be unique across all devices.

• You cannot:

  • Use these parameters when you create an in-memory device: vstart, cntrltype, dsync, directio, and skip_alloc.

  • Create an in-memory device that is larger than the cache on which it is created.

  • Create an in-memory device from a regular named cache, including the default data cache.

  • Increase the size of an in-memory device once it is created. However, you can use sp_cacheconfig to increase the size of the in-memory cache, and use disk init to create new in-memory devices.

  • Use these commands against in-memory devices: disk resize, disk mirror, disk remirror, disk unmirror, disk refit, and disk reinit.

  • Use the sp_deviceattr and sp_diskdefault system procedures on disk devices.

The directio parameter is ignored for raw devices.

Standards

ANSI SQL – Compliance level: Transact-SQL extension.

Permissions

disk init permission defaults to System Administrators and is not transferable. You must be using the master database to use disk init.

Auditing

Values in event and extrainfo columns of sysaudits are:

See also