Physical storage on DASD with variable logging.

Products

• Datacom
• DATACOM - AD
• Common Components and Services for z/OS
• Common Services
• Datacom/DB

Issue/Introduction

What does variable logging mean in Datacom?

Resolution

Variable logging means Datacom will create blocks of LXX records with block size up to 32760.  It will always store these blocks as efficiently as possible regardless of the physical storage device type used. 

In Datacom, with variable logging, the maximum block size is set to 32760. MUF uses a variable size up to this maximum to ensure most efficient use of DASD. This is based upon the actual log records generated that need top be written to the LXX. In this process, usable space is not wasted on the tracks, regardless of the device type.

For Example:
With 3390 DASD tracks of 58786 bytes & LXX block size 32760, the first block will be up to (close to) the 32760 size. The second block will be close to 23K to fill the track.

There are exceptions to this, but the storage is always as efficient as Datacom can make it, regardless of the physical device type on which the log data is stored.