NAME

preview.cmd - Oracle HSM preview directives file

SYNOPSIS

∕etc∕opt∕SUNWsamfs∕preview.cmd

AVAILABILITY

SUNWsamfs

DESCRIPTION

An archive or stage request for a volume that is not currently loaded goes to the preview area for future consideration. A user can control the scheduling of preview requests, thus overriding the default behavior, by entering directives in the preview.cmd file.

The preview.cmd file contains directives for modifying preview request priorities. The directives allow users to increase the priority for specific VSNs and change archive request priorities based on the file system states regarding High Water Mark (HWM) and Low Water Mark (LWM). These directives are read by sam-amld at start-up time, and all values specified are stored in shared memory. The priority specifications cannot be changed while the sam-amld daemon is running.

The preview.cmd file can contain comments. A comment begins with a pound character (#) and extends through the end of the line.

DIRECTIVES

The directives in the preview.cmd file are specified one per line. With regard to their placement within the preview.cmd file, there are two types of directives:

Global directives. These directives apply to all file systems. Directives are assumed to be global if they appear in the preview.cmd file prior to any fs = directives.
Directives specific to a particular file system. File system specific directives must appear after the global directives in the preview.cmd file. A directive line with the following form names a specific file system and indicates that all subsequent directives apply only to that file system:
```
fs = file_system_family_set_name
```

A subsequent fs = directive in the preview.cmd file declares a set of directives that apply to another file system. File system specific directives override general directives.

Some directives can be used as both global and file system specific directives. This can be useful, for example, if you want to specify the hwm_priority directive globally to apply to most Oracle HSM file systems but you also want to use it as a file system specific directive to specify a different value for one particular file system.

The following sections describe the directives that can appear in a preview.cmd file. You can specify either an integer or a floating point value as an argument to the _priority directives, but the system stores the value as a floating point value internally.

Global Directives

Global directives must appear in the preview.cmd file before any fs = directives. They cannot appear after an fs = directive. The global directives are as follows:

vsn_priority = value

This directive specifies the value by which the priority is to increase for VSNs marked as high-priority VSNs. For more information, see the chmed (1m) man page. The vsn_priority = 1000.0 by default.

age_priority = factor

This global directive specifies a factor to to be applied to the time (in seconds) that a request is allowed to wait in the preview area to be satisfied. The factor is as follows:

A factor 1.0, increases the weight of the time when calculating the total priority.
A factor 1.0, decreases the weight of the time when calculating the total priority.
A factor = 1.0 has no effect on the default behavior. The age_priority = 1.0 by default.

For more information, see the PRIORITY CALCULATION section of this man page.

File System Specific Directives

The fs = directive specifies a particular file system and applies only to that specified file system. This directive's syntax is as follows:

fs = file_system_family_set_name: This directive indicates that the subsequent directives apply only to the indicated file_system_family_set_name.

Global or File System Specific Directives

Several directives can be used either globally or as file system specific directives. These directives are as follows:

hwm_priority = value: This directive indicates the value by which the priority is to increase for archiving requests versus staging after the file system crosses the HWM level. This means that the releaser is running. The hwm_priority = 0.0 by default.
hlwm_priority = value: This directive indicates the value by which the priority is to increase for archiving requests versus staging. This directive is effective when the file system is emptying, and the amount of data is between the HWM and the LWM. Because the file system is emptying, you may want to give priority to loads for stage requests. The hlwm_priority = 0.0 by default.
lhwm_priority = value: This directive indicates the value by which the priority is to increase for archiving requests versus staging. This directive is effective when the file system is filling up, and the amount of data is between the HWM and the LWM. Because the file system is filling up, you may want to give priority to loads for archive requests. The lhwm_priority = 0.0 by default.
lwm_priority = value: This directive specifies the value by which the priority is to increase for archiving requests versus staging when the file system is below the LWM level. The lwm_priority = 0.0 by default.

PRIORITY CALCULATION

The total preview request priority is the sum of all priorities and is calculated as follows:

Total priority = vsn_priority + wm_priority + age_priority * time_in_sec

The wm_priority in the previous equation refers to whichever condition is in effect at the time, either hwm_priority, hlwm_priority, lhwm_priority, or lwm_priority. All priorities are stored as floating point numbers.

EXAMPLES

Example 1. This example preview.cmd file sets both the vsn_priority and hwm_priority for the samfs1 file system. Other Oracle HSM file systems not specified here use the default priority for the HWM. All file systems use the default priorities for the LWM and the state between LWM and HWM.

vsn_priority = 1000.0
fs = samfs1
hwm_priority = 100.0

Example 2. The next example preview.cmd file sets priority factors for all Oracle HSM file systems, but it sets an explicit and different HWM priority factor for the samfs3 file system.

hwm_priority = 1000.0
hlwm_priority = -200.0
lhwm_priority = 500.0
fs = samfs3
hwm_priority = 200.0