IMSLIB_DSN keyword Use the IMSLIB_DSN keyword to specify the name of the production IMS SDFSRESL library. IMSLIB_DSN is a required keyword for the JCLPARM subcommand. Format: IMSLIB_DSN= 'dsname' dsname Specify a 1- to 44-character data set name. Enclose the data set name in single quotation marks ('). Default: None. Site default support: Not supported.