z/OS V1R9.0 TSO/E Command Reference

ALLOCATE commandUse the ALLOCATE command or the ALLOCATE subcommand of EDIT (thesubcommand’s function and syntax are identical to the ALLOCATE command) toallocate dynamically the VSAM and non-VSAM data sets, and UNIX files requiredby a program that you intend to execute. Each UNIX file system data set containszero or more UNIX files.Each UNIX file system data set has a 44-byte data set name and must becapitalized and cataloged. A UNIX file has a mixed-case name of up to 250characters.There is no documented API for an UNIX file system data set. Users can accessUNIX files with BSAM, QSAM, VSAM and UNIX calls.You can specify data set attributes for non-VSAM data sets that you intend toallocate dynamically in several ways:v Use the LIKE operand to obtain the attributes from an existing model data set (adata set that must be cataloged) whose data set attributes you want to use. Youcan override model data set attributes by explicitly specifying the desiredattributes on the ALLOCATE command.v Identify a data set and describe its attributes explicitly on the ALLOCATEcommand.v Use the ATTRIB command to build a list of attributes. During the remainder ofyour terminal session, you can have the system refer to this list for data setattributes by specifying the USING operand when you enter the ALLOCATEcommand. The ALLOCATE command converts the attributes into the data controlblock (DCB) operands for data sets being allocated. If you code DCB attributes inan attribute-list and you refer to the attribute-list using the USING operand on theALLOCATE command, any DCB attribute you code on the ALLOCATE commandis ignored.v With the Storage Management Subsystem (SMS) installed and active, use theDATACLAS operand. Your storage administrator might provide default data setattributes through the automatic class selection (ACS) routine. Using DATACLASto define the data class for the data set makes specifying all the attributesunnecessary.In this book, “with SMS” indicates that SMS is installed and is active. “Without SMS”indicates that SMS is not installed. Requesting space, in terms of a quantity oflogical records, is device-independent and is particularly useful in conjunction with asystem-determined BLKSIZE. This space can be obtained by omitting the BLKSIZEoperand and coding LRECL, RECFM, and DSORG, or acquiring these from SMSDATACLAS.Data sets with SMSIf your installation has the Storage Management Subsystem (SMS), and it is active,SMS allows you to more easily define new data sets by managing storagerequirements for you. The storage administrator at your installation determines thedata sets that are to be managed by SMS. The administrator writes the automaticclass selection (ACS) routine that SMS uses to assign definitions or classes to anew data set. See SMS classes.SMS can manage the following types of data sets:v Physical sequential data setsALLOCATE CommandChapter 1. TSO/E commands and subcommands 17