10.1 Chapter Objectives

• Prevent application downtime resulting from insufficient disk space

• Stabilize disk-space use

• Encourage automatic disk-space reclamation by OpenVMS and users

10.2 Introduction

Users depend heavily on the availability of disk space to create new files and extend existing ones. If a disk completely runs out of space, applications can fail, and the OpenVMS system itself may hang. To prevent application downtime, proper disk-space management is essential.

An effective disk-space-management strategy should consider the following issues:

• Current and future storage requirements and technologies

• Backup strategy

• Disk cluster size

• Purging files

• File version limits

• Disk quotas

• File expiration dates

• Volume rebuilds

• System log file archiving

• Bad blocks

Users may also monitor disk usage using commands described in this chapter and in chapter 11.

10.3 Current and Future Storage Requirements

Typically, applications grow as they are improved. This means that you must plan for the addition of storage, in particular for the addition or the replacement of existing storage devices with newer storage devices. This can also involve controller and cabinetry upgrades as storage technologies change. You will also often need to plan for the off-line or near-line archiving of older data and for the migration of existing data to newer storage.

As an example of technology upgrades, older DSSI disks and cabinetry were replaced with SCSI disks, then with Fast SCSI or with UltraSCSI disks, and then with Fibre Channel or other disk storage. These upgrades provide far faster disk access, far denser storage, and far better device lifetimes. Not...