To calculate the maximum number of data spaces that your database may use, follow the instructions for the type of mapping you are using (logical or physical). (Logical is the default and suggested type of mapping for most applications.)
If you are using logical mapping, you can calculate the maximum number of data spaces by selecting the correct formula from Figure 39. Substitute the total number of public, private, and internal dbspaces in your database into the formula. When appropriate also substitute the number of cylinders in your directory disk and the conversion factor for your directory disk's DASD type. (Use Table 14 to look up the directory conversion factor for your database.)
Table 14. Directory Conversion Factor (For use with 4KB directory pages)
|
DASD Type |
3350 |
3375 |
3380 |
3390 |
9345 |
|---|---|---|---|---|---|
|
Conversion Ratio |
4369 |
5461 |
3495 |
2912 |
3495 |
Consider a database where you are planning to use the directory with data spaces, and unmapped internal dbspaces. It has a total of 640,000 pages allocated to public and private dbspaces, and 80 internal dbspaces of 1024 pages each. It also has a 40-cylinder 3380 directory disk.
Choosing the bottom formula, you would perform the following calculation:
| Note: | If you have a storage constrained environment, please see Real Storage Requirements for Data Spaces. |
If you are using physical mapping, you can calculate the maximum number of data spaces from the results of a SHOW POOL operator command. Add the total number of pages in each pool to the total number of pages in free areas (deleted dbextents) and substitute this number into the correct formula in Figure 40. When appropriate also substitute the number of internal dbspace pages, the number of cylinders in your directory disk, and the conversion factor for your directory disk's DASD type. (Use Table 14 to look up the directory conversion factor for your database.)
Consider a database where you are not planning to use the directory with data spaces or unmapped internal dbspaces. The following SHOW POOL was performed for the database:
+--------------------------------------------------------------------------------+ |show pool | | | |POOL NO. 1: NUMBER OF EXTENTS = 3 | | | |EXTENT TOTAL NO. OF NO. OF NO. OF % | |NO. PAGES PAGES USED FREE PAGES RESV PAGES USED | | 1 285 274 11 96 | | 2 285 33 252 11 | | 6 741 0 741 0 | |TOTAL 1311 307 1004 20 23 | | | |POOL NO. 2: NUMBER OF EXTENTS = 3 | | | |EXTENT TOTAL NO. OF NO. OF NO. OF % | |NO. PAGES PAGES USED FREE PAGES RESV PAGES USED | | 3 114 2 112 1 | | 4 114 0 114 0 | | 9 114 0 114 0 | |TOTAL 342 2 340 20 0 | | | |POOL NO. 4: NUMBER OF EXTENTS = 1 SHORT ON STORAGE | | | |EXTENT TOTAL NO. OF NO. OF NO. OF % | |NO. PAGES PAGES USED FREE PAGES RESV PAGES USED | | 10 285 260 25 91 | |TOTAL 285 260 25 20 91 | | | | | |FREE AREAS: NUMBER OF DELETED EXTENTS = 3 | | | |EXTENT TOTAL | | NO. PAGES | | (2+) 57 | | 5 171 | | 7 228 | | 8 342 | | END 9552 | |TOTAL 10350 | | | |Maximum number of DBEXTENTs = 64 | |ARI0065I Operator command processing is complete. | +--------------------------------------------------------------------------------+
By adding the underlined values you get the total number of data spaces pages required.
1311
342
285
57
171
228
+ 342
2336 data space pages
Since this number is less than 524288, you will only require one data space. (Select the first formula. Divide 2336 by 524288 and round up to the nearest integer.)
| Note: | If you have a storage constrained environment, please see Real Storage Requirements for Data Spaces. |