Top 10 best sas programming practices short summary. Understanding and using the macro facility tree level 1. The program data vector contains two types of variables. It takes each observation at a time and allocates the length given in the. When the data step reads a sas data set, sas reads the data directly into the program data vector. Hi all, i am running a sas program that converts report to pdf. She says that when you want to do complex processing, youll want want concrete knowledge of what the pdv is holding and the rules sas observes in manipulating that information.
As was said before, using the debugger is the process of comparing what is. Understanding the sas pdv in bygroup processing stack. A sas array is a temporary grouping of sas variables under a single name. How to use sas special topic macro coding and macro variables duration. The pdv is a logical area in memory with four physical memory locations and all calculations happen inside the program data vector. Sas execution phase program data vector pdv output to a sas data set. Variables not read into the pdv are not available for processing. If the input file contains raw data as in the example above, sas creates an input buffer to hold the data before moving the data to the program data vector pdv. Sas sets the newly created program variables to missing in the program data vector pdv. If sas is processing olddata rowbyrow, how is the pdv aware that the next row holds another group a observation instead of a new group.
The pdv is an internal record in memory where data is held while its being processed through the data step. Sas uses the pdv, a memory area on your computer, to build the new data set. Pdv, variablen, initialisierung, fallstricke, datastep, debug. Sas pdv vector maziworld sas online training videos. The pdv is where sas builds the data set, one observation at a time. During compilation, sas parses the code to check for correct syntax and to setup the program data vector. Through innovative analytics, artificial intelligence and data management software and services, sas helps turn your data into better decisions. Sas reads a data record from a raw data file into the input buffer, or it reads an observation from a sas data set directly into the program data vector. This paper describes the compile and execution phases as well as the pdv. This course is part of a series by the sas institute, designed to prepare you for the sas 9. The report is big 150807 lines and i getting out of memory error. The program data vector is unusual in that it exists in the compile step as well as in the execution phase of a sas job. After processing all the observations from one by group, sas expects the next observation to be from the next by group. Use of drop, keep, where, and rename will affect the program data vector and can have a profound effect on the operation of sas.
The program data vector is a logical area of memory that is created during the data step processing. Sas provides the following flowchart to describe the processing of the data step1. Variables in the pdv are initialized, the data step program is called, the user controlled data step machine code statements are executed, and the default output of observations is handled. When the data step is compiled, the pdv is created containing all variables on the input sas. Introduction this tutorial discusses the functions of sas supervisor during execution a. During processing, the data step also generates certain automatic variables that can be used for further processing.
She says that when you want to do complex processing, youll want want concrete knowledge of what the pdv is holding and the rules sas. Introduction this tutorial discusses the functions ofthe sas supervisor during the execution ofa sas data step program and is a repeat presentation of a paper given in the tutorial and the advanced tutorial sessions of sugi 12. Sas builds a sas dataset by reading one observation at a time into the pdv and, unless given code to do otherwise, writes the observation to a target dataset. The output datasets are created empty only then is. Sas also creates the program data vector pdv in the compilation phase figure 1. Sas executes any other programming statements for the current record. This video will explain you how sas reads the data in background. The secret life of data step swati agarwal, optum, eden. Use the in option on the merge statement to control processing. The program data vector, or pdv, is a temporary area in memory which sas. The pdv is a logical concept in data step programming beoptimized. At compile time, the program data vector pdv is initialized.
The sas supervisor don henderson merry rabb ori, inc. Managing and making sense of data streams to make realtime decisions on streaming data, its important to process and provide deep analysis on data at a very high throughput speed. Sas reads data from an input file or from a sas data set directly into the program data vector, replacing the previously existing values. Do loop processing do loop processing statements within a do loop execute for a specific number of iterations or until a specific condition stops the loop. Processing all the rows and columns in a file automatically opening and closing of files.
Sas reads a data record from a raw data file into the input buffer there are other possibilities not discussed here. Sas reads a data record from a raw data file into the input buffer, or it reads an observation from a sas. When a program executes, sas reads data values from the input buffer or creates them by executing sas. Data statement sas statements do statement iterated sas statements end statement sas statements run statement do loop processing. Sas data step powerpoint presentation in pdf format.
In other words, it seems like sas must be using information from previous or future rows to update the first and last variables, but im not sure how. This paper is for those who have spent some time in sas, understand the basics of the program data vector pdv and are ready to move forward in their sas experience. The pdv, the holder of information while sas is executing the data step, is the core of this. Arthur xuejun li, city of hope national medical center, duarte, ca. The sas system returns to the beginning of the data step to begin the second iteration. If the input file is a sas data set, however, sas does not create an input buffer. Then, they become available for data step processing but sas. Here you can explore data processing techniques using the sas data step. Instructor stacey syphus provides demos of data step processing in action, showing what goes on behind the scenes in sas. When data step statements are compiled, sas determines whether to create an input buffer.
Program data vector pdv is created and contains information about the variables. The pdv, which stands for program data vector, is a key data step concept. It exists only for the duraon of the data step useful for processing several variables at the same me. Sas book the pdv contains all the variables in the input data set, the variables created in. Beginning programmers often tend to focus on learning syntax without understandinghow sas. By understanding the default activities of the data step, the sas programmer.
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