If the LOB table space is compressed because it is defined with the COMPRESS YES option,  DSN1COMP collects statistics of the individual LOB metadata from the LOB map pages and  produces a report without collecting and compressing data by using the zEDC card again. Db2 does not compress LOBs that are less than the current page size that is used for the  object. In addition, different types of files have different compression ratios. Therefore, it is  useful to estimate how much your LOBs can be compressed by checking the compression  ratio and data pages that are saved by using the DSN1COMP utility before compression on  those LOBs is implemented. Db2 does not support compressing individual pieces of a linear data set. Also, because LOB  table spaces are linear page sets, compression applies to the entire (non-partitioned) LOB  table space. Therefore, all of the pieces (A001, A002, and so on) should be evaluated for  compression savings by using DSN1COMP. However, for DSN1COMP, it is sufficient to  specify only the A001 data set on the SYSUT1 DD-statement. Db2 finds the other pieces if  they exist. A non-partitioned table space must contain all pieces when an image copy of the LOB table  space is used as input to DSN1COMP.  For a partitioned table space, the image copy can contain a single partition, a subset of  partitions, or all partitions. A sample JCL statement that can be used to estimate space savings for a (currently  uncompressed) LOB table space that uses DSN1COMP is shown in Example 3-1. Excerpts  from the report that is produced also are shown. Example 3-1 Sample output for uncompressed LOB table space Chapter 3. Synergy with the IBM Z platform  87 JCL: //COMP1 EXEC PGM=DSN1COMP,PARM='LOB' //SYSUT1 DD DISP=SHR,DSN= DSNC000.DSNDBC.MYLOBDB.MYLOBTS1.I0001.A001  Output: DSN1999I START OF DSN1COMP FOR JOB DSN1CMP STEP2 DSN1998I INPUT DSNAME = DSNC000.DSNDBC.MYLOBDB.MYLOBTS1.I0001.A001 , VSAM DSN1944I DSN1COMP INPUT PARAMETERS PROCESSING PARMS FOR LOB DATASET: NO PARAMETERS. DSN1940I DSN1COMP COMPRESSION REPORT  DSN1COMP run on uncompressed LOB table space  LOB table space statistics  ---------------------------------------------------------  Number of LOBs 200 LOBs  Minimum LOB size 3 KB  Maximum LOB size 28 KB  Average LOB size 25 KB  LOB compression ratio  ---------------------------------------------------------  Total LOB data compressed 2,195 KB  Total LOB data uncompressed 5,143 KB  Percentage of KB saved 58 %  Data pages needed for compressed LOB table space 371 Pages  Data pages needed for uncompressed LOB table space 1,090 Pages  Percentage of Data pages saved 66 %  Current page size 4 KB  EVALUATION OF COMPRESSION WITH DIFFERENT PAGE SIZES  Note: System Pages may contain LOB data!