Is there a formula to calculate the INDEX and DATA extents in View?
Release: 12.1
Estimate the size of the View r11 Index component:
Note: A good guideline for the index size is to compute the amount of space used by View 2.0.
Run the SARDBASE/STATUS FULL function:
//STEP1 EXEC PGM=SARDBASE
//STEPLIB DD DISP=SHR,DSN=........VIEW.CAILIB
//SYSPRINT DD SYSOUT=*
//SYSIN DD *
NAME ........db_hlq..........
STATUS FULL
/*
Use the following output from this step:
SARDBA09 BLOCK SIZE: nnnnn
SARDBA09 INDEX USED BLOCKS: nnnnn
SARDBA09 INDEX EMPTY BLOCKS: nnnnn
(INDEX USED BLOCKS - INDEX EMPTY BLOCKS) *
BLOCK SIZE = bytes_used
((bytes_used / 8906) / 90) * 2 = cylinders
8906 is the recommended block size for the Index component in r11 and 90 is the number of blocks
per cylinder for a 3390 Device. This number should be doubled.
As an example:
BLOCK SIZE: 3476
INDEX USED BLOCKS: 1522838
INDEX EMPTY BLOCKS: 419345
(1522838 - 419345) * 3476 = 3,835,741,668 bytes
((3835741668 / 8906) / 90) * 2 = 9570 cylinders
(INDEX USED BLOCKS / TOTAL USED BLOCKS) * 100 =
Index Utilization Percentage
Example:
SARDBA09 TOTAL USED BLOCKS: 3594869
Although the space originally occupied by the index component is totally re-useable
for Sysouts in the data extent, it is highly unlikely that this space (as in the example
70% of the original database) is needed since it was used by the index.
A procedure to consider is:
Data Extent Allocation Example:
The View 2.0 Database has 1,117,740 Blocks at a Block Size of 3476. The Index occupied
566,023 Blocks:
SARDBA09 BLOCK SIZE: 3476
SARDBA09 TOTAL BLOCKS: 1117740
SARDBA09 INDEX BLOCKS: 566023
The new Data Extent size can be computed with the following formula:
(Total Blocks - INDEX Blocks) * Block Size = Data Space Allocation
((Data Space Allocation / New Block Size)) / Block Per Cylinder = Cylinders
The Block Size for the new Data Extent should be specified as 13,682, which is the recommended
| data extent block size. Using the sample data, assuming 60 Blocks per 3390 Cylinder:
(1117740 - 566023) * 3476 = 1917768292
((1917768292 / 13682) / 60 = 2336 Cylinders