Physical storage on DASD with variable logging.

Document ID : KB000028431
Last Modified Date : 14/02/2018
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Description:

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

Solution:

According to the CA Datacom/DB DBUTLTY Reference Guide, the section titled "Init CXX/FXX/IXX/LXX/WXX/Data Area > Init LXX (Format Log Area) > When to Use > Variable Log Area (LXX) Block Size" reads as follows: "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, we do not waste usable space on the tracks, regardless of the device type.

With 3390 DASD tracks of 58786 bytes & LXX block size 32760, for example, the first block will be up to (close to) the 32760 size. We put in as many log records as will fit in that 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.

For more information about the use of variable block size for the LXX, please refer to the CA Datacom/DB Database and System Administration Guide, in the section "Using Logging", in the subsection "Variable Log Area (LXX) Block Size."