Data Set Statistics report

This report provides physical statistics about the database by each data set group.

The following figure shows an example of the Data Set Statistics report for an HDAM database.

Figure 1. Data Set Statistics report (for an HDAM database)

IMS HIGH PERFORMANCE LOAD                                          PAGE:       1 
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                            "DATA SET STATISTICS"                                
                                                                                 
DBNAME = DBHD0030  DS GROUPS = 3       ORG = HDAM          ACCESS METHOD = ESDS  
RMNAME = DFSHDC40  NBR OF RAPS = 5     MAX RBN= 500        MAX INSERT=40  
                                                                                 
DS GROUP = 001 OF 003   DDNAME = DDHD0031    BLKSIZE = 4,096     LRECL = 4,089   
 DISTRIBUTED FREE SPACE = (000,00)     SCAN = 3                                  
 THRESHOLD OF LIMITED FREE SPACE BLOCK     =  2,000 (LARGE SEGSZE 2,000)         
 NUMBER OF TOTAL BLOCKS                    =  501                                
 NUMBER OF BITMAP BLOCKS                   =  1                                  
 NUMBER OF LIMITED FREE SPACE BLOCKS       =  1                                  
 NUMBER OF FULL BLOCKS                     =  1                                  
 NUMBER OF FREE BLOCKS                     =  489                                
 AVERAGE SIZE OF FREE SPACE ELEMENT        =  4062.6                             
                                                                                 
 NUMBER OF HDAM ROOT SYNONYM CHAINS        =  0                                  
 AVERAGE NUMBER OF ROOTS / SYNONYM CHAIN   =  0.0                                
 NUMBER OF ROOTS NOT ON SYNONYM CHAINS     =  10                                 
 NUMBER OF ROOTS ON SYNONYM CHAINS         =  0                                  
 NUMBER OF ROOTS OUT OF RANDOMIZED BLOCK   =  0                                  
 NUMBER OF HDAM RAPS USED                  =  10                                 
 NUMBER OF HDAM RAPS UNUSED                =  2,490                              
 NUMBER OF HDAM OVERFLOW BLOCKS            =  1                                  
                                                                                 
 NUMBER OF SEQUENTIAL WRITES               =  502                                
 NUMBER OF DIRECT READS                    =  1                                  
 NUMBER OF DIRECT WRITES                   =  1                                  
                                                                                 
 NUMBER OF DSPB ROUTINGS                   =  0                                  
 HIGHEST LENGTH OF DATA IN DSPB            =  0                                  
 AVERAGE LENGTH OF DATA IN DSPB            =  0.0                                
                                                                                 
DS GROUP = 002 OF 003   DDNAME = DDHD0032    BLKSIZE = 512       LRECL = 505     
 DISTRIBUTED FREE SPACE = (000,00)     SCAN = 3                                  
 NUMBER OF TOTAL BLOCKS                    =  3                                  
 NUMBER OF BITMAP BLOCKS                   =  1                                  
 NUMBER OF LIMITED FREE SPACE BLOCKS       =  2                                  
 NUMBER OF FULL BLOCKS                     =  1                                  
 NUMBER OF FREE BLOCKS                     =  0                                  
 AVERAGE SIZE OF FREE SPACE ELEMENT        =  133.0                              
                                                                                 
 NUMBER OF SEQUENTIAL WRITES               =  4                                  
 NUMBER OF DIRECT READS                    =  1                                  
 NUMBER OF DIRECT WRITES                   =  1                                  
                                                                                 
 NUMBER OF DSPB ROUTINGS                   =  0                                  
 HIGHEST LENGTH OF DATA IN DSPB            =  0                                  
 AVERAGE LENGTH OF DATA IN DSPB            =  0.0                           
DS GROUP = 003 OF 003   DDNAME = DDHD0033    BLKSIZE = 1,024     LRECL = 1,017  
 DISTRIBUTED FREE SPACE = (000,00)     SCAN = 3                                 

IMS HIGH PERFORMANCE LOAD                                          PAGE:       2
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                            "DATA SET STATISTICS"                               
                                                                                
 NUMBER OF TOTAL BLOCKS                    =  5                                 
 NUMBER OF BITMAP BLOCKS                   =  1                                 
 NUMBER OF LIMITED FREE SPACE BLOCKS       =  4                                 
 NUMBER OF FULL BLOCKS                     =  1                                 
 NUMBER OF FREE BLOCKS                     =  0                                 
 AVERAGE SIZE OF FREE SPACE ELEMENT        =  161.5                             
                                                                                
 NUMBER OF SEQUENTIAL WRITES               =  6                                 
 NUMBER OF DIRECT READS                    =  1                                 
 NUMBER OF DIRECT WRITES                   =  1                                 
                                                                                
 NUMBER OF DSPB ROUTINGS                   =  0                                 
 HIGHEST LENGTH OF DATA IN DSPB            =  0                                 
 AVERAGE LENGTH OF DATA IN DSPB            =  0.0

The report shows the following items for each data set group. These items are common to HDAM, HIDAM, HISAM, SHISAM, PHDAM, and PHIDAM databases, except for those specified.

The first line contains database information found in the DBD, such as the database name, number of data set groups, organization type, and access method. If the organization type of the reloaded database is HISAM or SHISAM, the ddname, block size, and record length are reported in these lines.
The second line provides information about the randomizing module. This information is provided only for HDAM and PHDAM databases.
- RMNAME specifies the 1- to 8-character alphanumeric name of the randomizing module.
- MAX INSERT is the maximum number of bytes of a database record that can be inserted into the root addressable area.
- NBR OF RAPS specifies the number of root anchor points desired in each control interval or block in the root addressable area.
- MAX RBN is the maximum relative block number value.
The first line of each data set group indicates the data set information, such as data set group number, ddname, block size, and record length.

DISTRIBUTED FREE SPACE: The free block frequency factor (fbff) and the free space percentage factor (fspf). fbff can be any integer value in the range of 0 - 100 except fbff=1. The fspf specifies the minimum percentage of each control interval or block that is to be left as free space. fspf is in the range of 0 - 99.
THRESHOLD OF LIMITED FREE SPACE BLOCK: The threshold value used to set bitmap that indicates whether each block or CI has a free space element (FSE) that is large enough. If BMSETDSG control statement is specified, the specified value is shown instead of the size of the largest segment in the data set group.
SCAN: The number of direct-access device cylinders to be scanned when searching for available storage space during segment insertion operations.
NUMBER OF TOTAL BLOCKS: The total number of blocks or CIs written in the data set. If this data set is a VSAM data set, it does not include record 0.
NUMBER OF BITMAP BLOCKS: The total number of bitmap blocks or CIs written in the data set.
NUMBER OF LIMITED FREE SPACE BLOCKS: The number of blocks or CIs that do not have a free space element (FSE) large enough to hold the largest segment in the data set group.
NUMBER OF FULL BLOCKS: The number of blocks or CIs that do not have enough free space for an FSE. An FSE requires a minimum of 8 bytes.
NUMBER OF FREE BLOCKS: The number of blocks or CIs that do not have any segments in the data set group.
AVERAGE SIZE OF FREE SPACE ELEMENT: The average amount of free space in those blocks that are not completely full. This average includes those blocks that are completely empty.
NUMBER OF SEQUENTIAL WRITES: The number of sequential write operations to the database data set.
NUMBER OF DIRECT READS: The number of direct read operations to the database data set.
NUMBER OF DIRECT WRITES: The number of direct write operations to the database data set.

The following items are printed only for HDAM databases:

NUMBER OF HDAM ROOT SYNONYM CHAINS: The number of HDAM root anchor points (RAPs) that have more than one root segment chained off it.
AVERAGE NUMBER OF ROOTS / SYNONYM CHAINS: The average number of HDAM root segments per synonym chain.
NUMBER OF ROOTS NOT ON SYNONYM CHAINS: The number of HDAM root segments that are not on any synonym chain.
NUMBER OF ROOTS ON SYNONYM CHAINS: The number of HDAM root segments that are on one of synonym chains. A relatively high number here might have an impact on performance.
NUMBER OF ROOTS OUT OF RANDOMIZED BLOCK: The number of root segments that were randomized to given blocks, but there was not enough space in the blocks to insert the segments. Those root segments that cannot be inserted in the root addressable area are placed in the overflow area. A relatively high number here might have an impact on performance.
NUMBER OF HDAM RAPS USED/UNUSED: The number of total RAPs that are used or not used. The number of RAPs used versus the number of root segments is one indication of the efficiency of the randomizing routine. Comparison of the number of root segments with the number of RAPs used and unused gives you one indication of how well your HDAM randomizer is working. It does not indicate how uniformly the roots are distributed.
NUMBER OF HDAM OVERFLOW BLOCKS: The number of blocks or CIs in the overflow area.

The following items are printed only for HISAM databases that have more than one hierarchical segment level.

NUMBER OF RECORDS WITH OVERFLOW CHAINS: The number of roots with overflow chains.
MAX NUMBER OF OVERFLOW CHAINS: The maximum number of VSAM ESDS roots chained off from one VSAM KSDS root.
MIN NUMBER OF OVERFLOW CHAINS: The minimum nonzero number of VSAM ESDS roots chained off from one VSAM KSDS root.
AVERAGE NUMBER OF OVERFLOW CHAINS: The average number of VSAM ESDS roots chained off from one VSAM KSDS root.
NUMBER OF RECORDS WITH NO OVERFLOW CHAINS: The number of roots without dependent chains.
LONGEST DB RECORD LENGTH: The largest database record (in bytes) that has no overflow chains.
SHORTEST DB RECORD LENGTH: The shortest database record (in bytes) that has no overflow chains.
AVERAGE DB RECORD LENGTH: Average database record length (in bytes) that has no overflow chains.
NUMBER OF DSPB ROUTINGS: The number of times that data is written to and from the data space buffer (DSPB).
HIGHEST LENGTH OF DATA IN DSPB: The maximum length of the data in DSPB.
AVERAGE LENGTH OF DATA IN DSPB: The average length of the data written into DSPB.