ACF Cache Session Summary Doubts

We are testing ACF 822 on zVSE4.3…

Please, does anyone know how are these values calculated?

How is “Current Adabas Buffer Efficiency” calculated?
How is “Estimated NON-CACHE Buffer Efficiency” calculated?
What are “Cache Spaces”? (We have 4 active Cache Spaces and 3 Dataspaces, according to query dspace)


12:22:31 ***** A D A B A S CACHING FACILITY ***** 2012-02-16
DBID 152 - Cache Session Summary - PCF0002
File Level
Cache Allocation Summary Page 1
Current Adabas Buffer Efficiency … 159,3
Estimated NON-CACHE Buffer Efficiency … 152,3
Number of Active Cache Spaces … 4
Number of Cache Spaces defined … 32

                        --- ASSO ---      --- DATA ---      --- WORK ---    

Cache Statistics
Cache writes … 177 93 0
Read EXCPS … 238 1827 0
Cache reads … 140 0 0
Total reads … 378 1827 0
Efficiency … 37,0 0,0 0,0

Read Ahead Statistics
RABN’s read … 197 0
EXCPS … 20 0
Ave. blks/EXCP … 9,8 0,0 next page >>

F1 Help:
13:22:48 ***** A D A B A S CACHING FACILITY ***** 2012-02-16
- Help Information - HCHSD02

                          GENERAL CACHE SUMMARY                     Page 1  

This function provides statistical information for ALL CACHE Spaces.

Cache Statistics
Cache writes - the number of RABNs moved from the Buffer Pool into Cache
Read EXCPS - actual READ I/O requests for RABN’s in the specified range
Cache reads - the number of read requests which were satisfied with a
RABN found in the CACHE as opposed to a READ EXCP being done
Total reads - Total of Read EXCPS + Cache reads; indicating EXCPs saved.
Efficiency - Cache effectiveness; calc as Cache Reads / Total Reads * 100

Read Ahead Statistics
RABN’s Read - number of reads when more than one RABN is read into cache
EXCPS - number of physical I/Os done
Ave.blks/EXCP - average number of blks read per EXCP.

Press ENTER to continue

query dspace
AR 0015 DEFINED: 20480K 256 16 5 1 960K
AR 0015 ACTUAL: 11488K 12 4 4 1
AR 0015
AR 0015 BG 1 FB 4 F3 4 S2 3
AR 0015
AR 0015 MFRAME(31): 0( 0)
AR 0015
AR 0015 1I40I READY

The layout you are displaying seems to be from Adabas Version 81 and not from 82.

In 82 the display has changed a little bit to be more precise:

09:42:00 ***** A D A B A S CACHING FACILITY ***** 2012-03-12
DBID 230 - Cache Session Summary - PCF0002
File Level
Cache Allocation Summary Page 1
Current Adabas Buffer Efficiency … 41.3
Projected NON-CACHE Buffer Efficiency … 33.2
Number of Active RABN ranges … 10
Number of RABN ranges defined … 15

Here is an explanation of the values:

Current Adabas Buffer Efficiency:
Adabas buffer efficiency calculated by the Adabas nucleus. The number of requested reads divided by the number of actual reads.

Projected (in your case still estimated) NON-CACHE Buffer Efficiency:
This number postulates the Adabas buffer efficiency if caching were not active. The number is calculated by adding all of the CACHE READS (that is, EXCPs saved) to the total number of actual reads for the nucleus

ACTIVE RABN RANGES (in your case number of active cache spaces)
The number of RABN ranges currently active and servicing I/O requests.

RABN RANGES DEFINED (in your case number of cache spaces defined)
The number of RABN ranges currently defined to the system.

When you define files (as you did) the RABN ranges are automatically calculated based on the file extents, i.e. in my example above I have defined one file, but it is spread over 15 extents (RABN ranges) and the program which I did run did not access all data in the file which is located in 10 different extents. From the main menu to ´F´- Files with Caching you can find more information about the allocations.

Thanks a lot.
Now I understand why these efficiencies are greater than 1 or 100%. For example, I understand that a Buffer Efficency of 50 means a efficency of 98% (or 0.98) (1-1/Buffer Efficiency)

Just for information: we are running Adabas 8.2.
(Adabas 8.2.3, AOS 8.2.3, ACF 8.2.2, Natural 8.2.2)