disk init

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

• device_name – is the name of the database device or file. The name must conform to the rules for identifiers and must be enclosed in single or double quotes. This name is used in the create database and alter database commands.
• physical_name – is the full specification of the database device or cache. This name must be enclosed in single or double quotes. When the physical device path is relative, disk init returns a warning.
• cache_name – name of the cache on which you are creating the disk.
• inmemory – indicates you are creating an in-memory device.
• skip_alloc – is a Boolean parameter for the disk init command. It is supported for devices created on non-Windows file systems and on Windows raw systems. When skip_alloc is set to true, users can avoid initialization of pages with zeros. The default of skip_alloc is false.
• vdevno – is the virtual device number, which must be unique among the database devices associated with the SAP ASE server. The device number 0 is reserved for the master device. Otherwise, valid device numbers must be between 1 and 2,147,483,647.

  To determine the virtual device number, look at the device_number column of the sp_helpdevice report, and use the next unused integer.

• size – is the amount of space to allocate to the new device. The following are example unit specifiers, using uppercase, lowercase, and single and double quotes interchangeably: ‘k’ or “K” (kilobytes), “m” or ‘M’ (megabytes), “g” or “G” (gigabytes), and ‘t’ or ‘T’ (terabytes). You should always include a unit specifier. Quotes are optional if you do not include a unit specifier. However, you must use quotes if you include a unit specifier. Acceptable values are:

  • 5120 = 10MB

  • "5120" = 10MB

  • "10M" = 10MB

• vstart – is the starting virtual address, or the offset, for the SAP ASE server to begin using the database device. The following are example unit specifiers, using uppercase, lowercase, and single and double quotes interchangeably: ‘k’ or “K” (kilobytes), “m” or ‘M’ (megabytes), “g” or “G” (gigabytes), and ‘t’ or ‘T’ (terabytes). You should always include a unit specifier. Quotes are optional if you do not include a unit specifier. However, you must use quotes if you include a unit specifier.

  The size of the offset depends on how you enter the value for vstart.

  • If you do not specify a unit size, vstart uses 2K pages for its starting address. For example, if you specify vstart = 13, the SAP ASE server uses 13 * 2K pages as the offset for the starting address.

  • If you specify a unit value, vstart uses the unit value as the starting address. For example, if you specify vstart = "13M", the SAP ASE server sets the starting address offset at 13MB.

  The default value (and usually the preferred value) of vstart is 0. If the specified device does not have the sum of vstart + size blocks available, the disk init command fails. If you are running the Logical Volume Manager on an AIX operating system, vstart should be 2. Specify vstart only if instructed to do so by SAP Technical Support.

• cntrltype – specifies the disk controller. Its default value is 0. Reset cntrltype only if instructed to do so by SAP Technical Support.
• dsync – specifies whether writes to the database device are flushed to the storage media, or are buffered only when using operating system files. This option is meaningful only when you are initializing an operating system file; it has no effect when initializing devices on a raw partition. By default, all operating system files are initialized with dsync set to true.
• directio – allows you to configure the SAP ASE server to transfer data directly to disk, bypassing the operating system buffer cache. The SAP ASE server passes the device options to Backup Server, which enables Backup Server to access the database device with the appropriate directio option.

  directio is a static parameter that requires a restart of the SAP ASE server to take effect.

  By default, directio is set to false for nonclustered SAP ASE servers, and to true for clustered SAP ASE servers.

  The directio parameter is ignored for raw devices.

• instance = "instance_name" – (clusters only) specifies the device as private and sets its owning instance to instance_name.

Examples

• Example 1 – Does not initialize pages with zeros:

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

  SAP ASE servers do 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. The SAP ASE 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

• Use block devices as a database device only on the HP-UX, Windows, and Linux platforms. disk init and disk reinit display a warning message if you attempt to create a block device on a different platform.

• Use skip_alloc to expedite crash recovery on non-NT file systems and on NT raw systems. Also, using skip_alloc with the directio feature creates devices faster and improves durability of updates. Regardless of space availability, skip_alloc always prints a warning message about making sure the SAP ASE server has the required space for future use.

• The master device is initialized by the installation program; you need not initialize this device with disk init.

• Devices created with disk init have restricted permissions.

• To successfully complete disk initialization, the “sybase” user must have the appropriate operating system permissions on the device that is being initialized.

• You can specify the size as a float, but the size is rounded down to the nearest multiple of 2K.

• If you do not use a unit specifier for size, disk init uses the virtual page size of 2K.

• The minimum size of a disk piece that you can initialize using disk init is the larger of:

  • One megabyte

  • One allocation unit of the server’s logical page size

• directio and dsync are mutually exclusive. If a device has dsync set to true, you cannot set directio to true for this device. To enable directio for a device, you must first reset dsync to false.

• directio is not available on all platforms. If you issue disk init with the directio parameter on a platform on which it is not supported, the SAP ASE server issues the message No such parameter: 'directio'.

• Use disk init for each new database device. Each time disk init is issued, a row is added to master..sysdevices. A new database device does not automatically become part of the pool of default database storage. Use sp_diskdefault to assign default status to a database device.

• Back up the master database with the dump database or dump transaction command after each use of disk init. This makes recovery easier and safer in case master is damaged. If you add a device with disk init and fail to back up master, you may be able to recover the changes by using disk reinit, then stopping and restarting the SAP ASE server.

• Assign user databases to database devices using the on clause of the create database or alter database command.

• The preferred method for placing a database’s transaction log (the system table syslogs) on a different device than the one on which the rest of the database is stored is to use the log on extension to create database. Alternatively, you can name at least two devices when you create the database, then execute sp_logdevice. You can also use alter database to extend the database onto a second device, then run sp_logdevice. The log on extension immediately moves the entire log to a separate device. The sp_logdevice method retains part of the system log on the original database device until transaction activity causes the migration to become complete.

• For a report on all SAP ASE devices on your system (both database and dump devices), execute sp_helpdevice.

• Use sp_dropdevice to remove a database device. You must first drop all existing databases on that device.

See also sp_diskdefault, sp_dropdevice, sp_helpdevice, sp_logdevice in Reference Manual: Procedures.

Standards

ANSI SQL – Compliance level: Transact-SQL extension.

Permissions

The permission checks for disk init differ based on your granular permissions settings. You must be using the master database to use disk init.

Auditing

Values in event and extrainfo columns of sysaudits are: