Sample DSN1COMP control statements

Use the sample control statements as models for developing your own DSN1COMP control statements.

Example 1: Estimating space savings from data compression for a full image copy

Start of changeThe following statement specifies that the DSN1COMP utility is to report the estimated space savings that are to be achieved by compressing the full image copy that is identified by the SYSUT1 DD statement. In this statement, the DSN value specifies the data set name of the image copy that is to be used as input. Because the input is a full image copy, the FULLCOPY parameter must be specified. End of change

//jobname JOB acct information
//COMPEST  EXEC PGM=DSN1COMP,PARM='FULLCOPY'
//STEPLIB  DD DSN=prefix.SDSNLOAD,DISP=SHR
//SYSPRINT DD SYSOUT=A
//SYSABEND DD SYSOUT=A
//SYSUT1   DD DSN=COPY001F.IFDY01,DISP=SHR

Example 2: Providing intended free space when estimating space savings

In the following sample statement, STEP1 specifies that DSN1COMP is to report the estimated space savings that are to be achieved by compressing the data in the data set that is identified by the SYSUT1 DD statement, DSNC810.DSNDBD.DB254SP4.TS254SP4.I0001.A00. When calculating these estimates, DSN1COMP considers the values passed by the PCTFREE and FREEPAGE options. The PCTFREE value indicates that 20% of each page is to be left as free space. The FREEPAGE value indicates that every fifth page is to be left as free space. This value must be the same value that you specified for the FREEPAGE option of the SQL statement CREATE TABLESPACE or ALTER TABLESPACE. 

STEP2 specifies that DSN1COMP is to report the estimated space savings that are to achieved by compressing the data in the data set that is identified by the SYSUT1 DD statement, DSNC810.DSNDBD.DB254SP4.TS254SP4.I0001.A0001. When providing the compression estimate, DSN1COMP is to evaluate no more than 20 000 rows, as indicated by the ROWLIMIT option. Specifying the maximum number of rows to evaluate limits the elapsed time and processor time that DSN1COMP requires.

Figure 1. Example DSN1COMP statements with PCTFREE, FREEPAGE, and ROWLIMIT options
//DSN1COMP JOB  MSGLEVEL=(1,1),CLASS=A,MSGCLASS=A,REGION=3000K,
//         USER=SYSADM,PASSWORD=SYSADM
/*ROUTE PRINT STLXXXX.USERID
//STEP1    EXEC PGM=DSN1COMP,PARM='PCTFREE(20),FREEPAGE(5)'
//STEPLIB  DD DSN=prefix.SDSNLOAD,DISP=SHR
//SYSPRINT DD SYSOUT=A
//SYSDUMP  DD SYSOUT=A
//SYSABEND DD SYSOUT=A
//SYSUT1   DD DSN=DSNC100.DSNDBD.DB254SP4.TS254SP4.I0001.A001,DISP=SHR
/*
//STEP2    EXEC PGM=DSN1COMP,PARM='ROWLIMIT(20000)'
//STEPLIB  DD DSN=prefix.SDSNLOAD,DISP=SHR
//SYSPRINT DD SYSOUT=A
//SYSDUMP  DD SYSOUT=A
//SYSABEND DD SYSOUT=A
//SYSUT1   DD DSN=DSNC100.DSNDBD.DB254SP4.TS254SP4.I0001.A001,DISP=SHR
/*
//

Example 3: Estimating space savings that are comparable to what the REORG utility would achieve.

The following statement specifies that DSN1COMP is to report the estimated space savings that are to be achieved by compressing the data in the data set that is identified by the SYSUT1 DD statement, DSNCAT.DSNDBD.DBJT0201.TPJTO201.I0001.A254. This input data set is a table space that was defined with the LARGE option and has 254 partitions, as indicated by the DSN1COMP options LARGE and NUMPARTS.

The REORG option indicates that DSN1COMP is to provide an estimate of compression savings that is comparable to the savings that the REORG utility would achieve, rather than what the LOAD utility would achieve.

When calculating these estimates, DSN1COMP considers the values passed by the PCTFREE and FREEPAGE options. The PCTFREE value indicates that 30% of each page is to be left as free space. The FREEPAGE value indicates that every thirtieth page is to be left as free space. This value must be the same value that you specified for the FREEPAGE option of the SQL statement CREATE TABLESPACE or ALTER TABLESPACE. DSN1COMP is to evaluate no more than 20 000 rows, as indicated by the ROWLIMIT option.

Figure 2. Example DSN1COMP statement with the LARGE, PCTFREE, FREEPAGE, NUMPARTS, REORG, and ROWLIMIT options.
Start of change
//STEP2  EXEC PGM=DSN1COMP,                                                 
//                  PARM='LARGE,PCTFREE(30),FREEPAGE(30),NUMPARTS(254),     
//             REORG,ROWLIMIT(1000)'                                   
//STEPLIB  DD DSN='USER.TESTLIB',DISP=SHR                                   
//         DD DSN='DB2A.SDSNLOAD',DISP=SHR                                  
//SYSPRINT DD SYSOUT=A                                                      
//SYSDUMP  DD SYSOUT=A                                                      
//SYSABEND DD SYSOUT=A                                                      
//SYSUT1   DD DSN=DSNCAT.DSNDBD.DBJT0201.TPJT0201.I0001.A254,DISP=SHR       
//SYSUT2   DD SYSOUT=A                                                      
/*
End of change
Start of change

Example 4: Building an Object Module from the DSN1COMP generated dictionary.

In the sample statement, BUILD specifies that DSN1COMP is to externalize the compression dictionary that it generated. This behavior is indicated by the EXTNDICT option, which requires that a DSN1DICT DD statement be provided. DSN1DICT identifies the output data set to which the generated object module is written and stored for additional processing.

Figure 3. Example DSN1COMP statement with the EXTNDICT option.
//BUILD    EXEC PGM=DSN1COMP,                                 
// PARM='DSSIZE(4G),EXTNDICT(dictname)'                       
//SYSPRINT DD  SYSOUT=A                                       
//SYSUT1   DD DSN=DSNCAT.DSNDBD.DBIA2401.TPIA2401.I0001.A254, 
//            DISP=SHR                                        
//DSN1DICT DD DSN=&&OBJ,                                       
//         DISP=(,PASS),                                       
//         UNIT=SYSALLDA,SPACE=(TRK,(8,4)),                    
//         DCB=(LRECL=80,BLKSIZE=4000,RECFM=FB)
End of change