Version 7.4.3
 —  Delta Save Facility Administration  —

Calculating the DLOG Area Size

Start of instruction setTo calculate a DSF logging area size (DLOGSIZE), use the following procedure as a guide:

  1. First, determine

  2. Calculate the approximate number of logged RABNs per DLOG block (LOGRABNS):

    graphics/ds_calc1.png

  3. Calculate the needed number of DLOG detail blocks (DLOGBLKS):

    graphics/ds_calc2.png

  4. Calculate the DLOG block count (DLOGRAW), including the security factor:

    
      DLOGRAW = DLOGBLKS + DLOGFAC
    
    

    The value DLOGSIZE is the calculated size of the DLOG area, in blocks.

Example:

The DLOG size is calculated using an average number of I/O operations between Delta Save operations of 1,000,000 based on a 3390 device type:

The approximate number of logged RABNs per block is

graphics/ds_calc4.png

The required detail blocks are calculated as

graphics/ds_calc5.png

The total DLOG block count including the security factor (in this case, 3) is calculated as


  1968 + 3 = 5904

-or 5904 blocks of DLOG area.

This value is entered in the "DLOG Area Size" field.

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