When executing multiple-step jobs, it is preferable to catalog or uncatalog data sets using JCL, instead of using IDCAMS, IEHPROGM, or a user program. Because step allocation and unallocation monitors data sets during job execution and is unaware of functions performed by user programs, conflicting functions can be performed or GDG orientation can be lost.

Unallocation can recatalog existing cataloged data sets at job termination. This action occurs when the data set is opened during the job and the DSCB TTR could not be found in the catalog entry. If you are using the CAMLST macro to uncatalog and then catalog data sets with new volume information, be sure to include the DSCB TTR.