DB2 and other RDBMS distinguish NULL from any possible actual value such as zero or a zero-length string.
Not sure of the size and signage of the field in question but -1 might have been a good indicator for "not set." Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Paul Gilmartin Sent: Tuesday, December 15, 2015 6:55 AM To: [email protected] Subject: Re: DFdss does not release space On Tue, 15 Dec 2015 13:00:31 +0000, Vernooij, CP (ITOPT1) - KLM wrote: >-----Original Message----- >From: Peter Hunkeler >Sent: 15 December, 2015 13:53 > >From the DSS Guide: >Chapter 9. Managing space with DFSMSdss Releasing unused space in data >sets ... >Exclude data sets whose last block pointer in the data set VTOC entry is not >maintained in the VTOC by using the EXCLUDE keyword. This can occur if you use >an access method other than BSAM, QSAM, BPAM, or VSAM. DFSMSdss does not >release space for data sets whose last block pointer in the data set entry is >0. > So the designers committed the unforgivable blunder of failing to differentiate between "0" and "unknown". This has been a problem for me elsewhere, in various DB interfaces, where I want to select all rows in which a certain column is unset, and get, in addition, those in which it is 0, or "", or some other default value. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
