Allocating and Formatting Files › Creating Disk Files

Creating Disk Files

Use Operating System Facilities

Use facilities provided by your operating system to create and catalog the files.

File Placement on Disk

You can reduce I/O response time by planning where you place files on a disk. In general, spread high activity files across disk devices and channels. Particularly, consider the placement of disk journal files used by systems engaged in high-volume update activity.

Multi-volume Files

CA IDMS does not support files that span multiple physical volumes. If an area is too large to reside on a single volume, it must be mapped to multiple files, each residing on a single physical volume.

Parallel Access Volume Exploitation

Parallel Access Volumes (PAV devices) allow concurrent I/O against individual files. If a database is allocated on a PAV device, it may reduce I/O wait times and thus increase transaction throughput and improve response times. Similar, although less significant, benefits may be achieved by allocating a journal file on a PAV device since I/O contention with the journal archive utility may be reduced.

No special action is needed to exploit this feature beyond allocating a database or journal file on a properly configured PAV device.

Valid Disk Devices for Archive and Tape Journal Files

The following table summarizes the disk device types CA IDMS/DB supports for archive and tape journal files:

Valid Device Types for Disk Journal Files and Database Files

The following table summarizes the device types CA IDMS/DB supports for disk journal files and database files:

Maximum Area Page Sizes

When allocating non-VSAM files in z/OS and z/VSE operating systems, the page size of an area is restricted by the track size of the disk device being used. The following table identifies the maximum page size for non-VSAM files in z/OS and z/VSE operating systems: