Download Multiple Engine Architecture: A Comparison of Database Management Systems Using the SAS/ACCESS Interface

THE MULTIPLE ENGINE ARCIIITECTURE:
A COMPARISON OF DATABASE MANAGEMENT SYSTEMS
USING THE SAS/ACCESS® INTERFACE
Alma Zuniga, SAS Institute Inc., Austin, Texas
ABSTRACT
system from within a SAS program, using the
descriptor files created with the ACCESS
procedure
SAS® System Version 6 architecture has opened up
new ways to interface the SAS® System with several
database management systems. Engines were a new
feature of Version 6 of the SAS System. These engines
retrieve data directly from files formatted by other
software vendors. This enables you to use SAS
procedures and program statements to process data
values stored in these files without the cost of
converting them into SAS data files. This paper will
compare the different database management systems
using the SASjACCESS® interface.
* extract data from a database management
system and place it in a SAS data file using the
ACCESS procedure or the DATA step
* load data into a database management system
using the DB LOAD procedure
* update data in a database management system
using the SQL procedure. SAS/FSP® software,
and the APPEND procedure.
INTRODUCTION
OVERVIEW OF USING THE INTERFACE
This paper discusses the purpose of the SAS/ACCESS
interface software. It will give you an overview of the
interface software and describe the procedures that
make up the software. The intent of the Mulitple
Engine Architecture is to access your data from your
database management system (DBMS) directly, without
having to create an intermediate SAS data file. Is the
SASjACCESS interface software similar across the
different software vendors? The differences, if any, are
discussed.
The SASjACCESS interface consists of three parts:
* the ACCESS procedure. which you use to define
the SASjACCESS descriptor files
* the interface view engine, which enables you to
use data from your database management system
in SAS programs in much the same way you use
SAS data files
* the DBLOAD procedure, which enables you to
create and load databases using data from SAS
data sets.
PURPOSE OF SAS/ACCESS SOFTWARE
SASjACCESS software provides an interface between
the SAS System and a database management system.
The Multiple Engine Architecture was designed to meet
several goals, including a transparent method of
accessing data stored in a database management
system. The SASjACCESS interface inc1udes an
interface view engine for reading and writing databases.
It also includes the ACCESS procedure for defming a
new type of SAS file called a descriptor file and the
DBLOAD procedure for creating and loading
databases. You can perform- the following tasks with
the SASjACCESS interface:
The ACCESS procedure enables you to describe data
from your database management system to the SAS
System. You store the description in SASjACCESS
descriptor files, which you can use in SAS programs
just as you would use SAS data files. You can print,
plot, and chart the data described by the descriptor
files, use them to create other SAS data files, and so- on.
The interface view engine is an integral part of the
SASjACCESS interface, but you do not have to deal
directly with the engine. The SAS System automatically
interacts with the interface view engine when you use
data from your database management system in your
SAS programs. You can simply use data from your
database management system just as you would use
SAS data.
* create SASjACCESS descriptor files using the
ACCESS procedure
*
access data directly in a database management
580
Engine Selection Window
lists all the available Version 6 SASjACCESS
interface products. installed on your machine.
This window appears only if you are creating an
access descriptor and you have more than one
Version 6 SASjACCESS interface product
installed on your system. If you have only one
Version 6 SASjACCESS interface product. the
Engine Selection Window does not appear and
you go directly to the Access Descriptor
Identification Window.
The DBLOAD procedure enables you to create and
load databases using SAS data.
SASfACCESS DESCRIPTOR FILES
To use the SAS/ACCESS interface with your database
management system software. you must define special
files that describe the database and data to the SAS
System. These files are called SAS/ACCESS descriptor
files. The two types of descriptor files are
* access descriptor files (member type access)
Access Descriptor Identification Window
begins the process of creating an access
descriptor. You use this window to specify the
database you would like to access. If all the
fields are filted in correctly, the information is
processed and the Access Descriptor Display
Window appears.
* view descriptor files (member type view).
An access descriptor contains information about the
database you want to use. The information includes
the database name, the items description, and their data
type. You use the access descriptor to build view
descriptors. You can think of an access descriptor as
being a master descriptor file for a single database
because it contains a complete description of the
database.
Access Descriptor Display Window
is used to define, edit, or browse an access
descriptor. You can choose SAS variable
names, formats, informats, ·and lengths, and
drop any items you do not want to appear in
the View Descriptor Display Window.
A view descriptor defines a subset of the data described
by an access descriptor file. You choose this subset by
selecting particular items. and you can specify selection
criteria that the data must meet. In most cases you can
even specify a sequence order for the data. After you
create your view descriptor files, you can use them in a
SAS program to read the data directly from the
database or to extract the data and place them in a
SAS data file. Typically, for each access descriptor that
you define, you have several view descriptors, each
selecting different subsets of data.
View
Descriptor Display Window
is used to derme, edit. or browse a view
descriptor. You choose SAS variable names.
formats, informats, and lengths if the access
descriptor has not assigned them with the
Assign Names = YES option.
Selection Criteria Entry Window
appears when the SUBSET command in the
View Descriptor Display Window is used. This
window is used to specify criteria for selecting
logical entries to be presented to the SAS
System and to specify a sort order for the data.
The SAS System sends the criteria you enter to
your database management system software to
be processed when you use the view descriptor.
ACCESS PROCEDURE
The A CCESS procedure is an interactive windowing
procedure that enables you to create and edit the
descriptor files used by the SAS/ACCESS interface to
your database management system. The procedure
consists of the following windows:
DBLOAD PROCEDURE
Access Window
enables you to create access descriptors and
view descriptors. as well as edit these files and
extract data by placing them into a SAS data
file. The Access Window lists all the files and
their associated librefs that are active during
your SAS session.
The DBLOAD procedure runs in interactive display
manager, interactive line, and batch modes. It enables
you to create and load a database using data from a
SAS data file, from a view created with the SQ L
procedure. or from another database (using a view
descriptor created with the ACCESS procedure). In
some cases you can submit SQL statements (except the
581
SELECT statement) to your database management
system for processing without leaving your SAS session.
The DBLOAD procedure enables you to
SAS /A CCESS software, an¥ SAS procedure, as well as
the DATA step. can access data from a database
management system directly, without having to create
an intermediate SAS data file. Version 6 also gives you
the option of extracting data from your database
management system. if that is better suited for your
applications. The SAS!ACCESS software is in
production for the following database management
systems:
* create a new database definition only
* create a new database defmition and load data
* load new logical entries into an existing database
* SYSTEM 2000® Data Management Software
lit insert new data records into existing logical
entries.
* DB2""
The DB LOAD procedures consists of the following
windows:
* SQL/DS'"
* ORACLE®
Engine Selection Window
lists all available Version 6 SASjACCESS
interface products installed on your machine.
This window appears only if you have more
than one Version 6 SASjACCESS interface
product licensed on your system. If you have
only one interface. this window does not appear
and you go directly to the Load Identification
Window.
Load
Identification Window
is used to identify the location of the input data
and specify information on the database that
you want to create.
Load
Display Window
is used to specify the items and data type
associated with each SAS variable. You can
also choose to load a subset of your input data.
* RdbjVMS""
* Prime INFORMATION""
OPERATING SYSTEMS
SYSTEM 2000 data management software is SAS
Institute's hierarchical database software for mainframe
computer systems running under MVS and CMS
operating systems.
DB2 is an IBM® relational database management
system that runs under the MVS operating system.
SQL/DS is an IBM® relational database management
system that runs under the eMS operating system.
Query Entry Window
can be invoked from either the Load
Identification Window or the Load Display
Window. The Query Entry Window enables
you to submit SQL statements to your database
management system without leaving the SAS
System.
ORACLE is Oracle Corporation's relational database
management system that runs under the VMS™
operating system.
MULTIPLE ENGINE ARCHITECTURE
Prime
INFORMATION
is
an
information
management system that runs under the PRIMOS®
operating system.
RdbjYMS is a relational database management system
created by the Digital Equipment Corporation (DEC®)
that runs under the VMS operating systems on VAXDl
machines.
In Version 5 software, you had to use a procedure to
extract data from your database management system
and place it in SAS data file before you could use the
i
data in a SAS program. In Version 6 of the SAS
System, the Multiple Engine Architecture was designed
to provide transparent access to data st~red in database
management systems of other vendors. In Version 6
a
CREATING AN ACCESS DESCRIPTOR
The ACCESS procedure allows you to create and edit
descriptor files and create output SAS data files. When
582
creating an access descriptor file. certain fields must be
filled in the Access Descriptor Identificaion Window.
The following fields are common in the interface
software for the database management systems:
program environment.
Database
enter Ibe name of Ibe SYSTEM 2000
database you want to use.
Library
is automatically filled in with the libref specified
in the PROC ACCESS statement or in the
Access Window command line. This can be
modified.
DB2
Authorization ID
is filled in with the authorization ID for the
table. If you do not specify an authorization
ID, it defaults to your userid.
Member
is automatically filled in with the member name
specified in the PROC ACCESS statement or in
the Access Window command line. The
member name for the access descriptor being
created can be modified.
Table Name
is filled in with the DB2 table or view name.
You must enter a value in this field.
SSID
is filled wilb Ibe DB2 subsystem ID. If yo'!
do not know the subsystem ID. contact your
DBA.
Type
has the value ACCESS because all access
descriptors have a member type of access. This
field cannot be edited.
SQLiDS
Assign Names
gives the option of standardizing SAS variable
names for subsequent view descriptors. The
default value NO penuits you to edit SAS
variable names. formats, informats. and lengths
when you create view descriptors. The value
YES gives the ACCESS procedure control of
assigning SAS variable names, formats.
informats. and lengths. This prevents you from
changing them when you create a view
descriptor.
Authorization ID
indicates the authorization ID for the
SQLiDS table. The aulborization ID is Ibe
SQL/DS userid of the table's creator. If you
do not fill in this field. it will default to your
userid.
Table Name
indicates the table or view you want to use.
You must enter a value in this field.
The following should be filled based on the database
management system:
User
SYSTEM 2000 Data Management Software
Password
enter a SYSTEM
four characters.
Display Window
components for
authorized.
2000 password of one to
The Access Descriptor
will contain only those
which the password is
ID
indicates the userid for the table or view you
want to use. If the table or view was created
under another person's userid, you must
enter a value in this field. If you fill in this
field, you must fill in the Password field.
Password
enter the password for the userid.
ORACLE
Multi-UserTM
specifies the execution environment that the
SYSTEM 2000 database exists in. YES, Ibe
default, specifies that the database exists in
the SYSTEM 2000 Multi-User environment.
NO specifies that the database exists in a
single-user environment, that is, your SAS
Table Name
enter the ORACLE table or view name.
You must enter a value in this field.User
583
Name
enter your ORACLE username.
Password
enter your ORACLE password. The
password is not displayed on the display.
Member
specify a member name for the view descriptor.
Rdb/VMS
Type
Database specify the location and name of the
Rdb/VMS database. It is recommended that
you use the fully qualified VMS filename sothat the access descriptor can be used from
any location. You must enter a value for
this field.
all
view
Output SAS Data Set: Library and Member
used when extracting data from your database
into a SAS data me. This is an optional field.
The following fields vary based on the database
management system being accessed:
Table Name
specify the RdbjVMS table or view name.
Y 00 must enter a value for this field.
SYSTEM 2000 Data Management Software
Prime INFORMATION
File
has the value VI EW because
descriptors are of member type view.
Database
taken from access descriptor.
cannot be edited.
Name
Prime
INFORMATION
specify
the
filename. You must enter a value in this
field; it cannot include the directory
specification.
This field
Password
is an optional. nondisplay field.
No
validation of the password is done at the
time.it is entered. An appropriate message
will result at the time the database is
accessed if the password is invalid. If a
password is not specified. one must be
provided at the time the database is accessed
by a SAS program with a data set option.
Vocabulary Path
fill in with a fully qualified pathname for the
vocabulary file. If the name does not
contain a directory specification, then only
your current directory will be searched.
After you fill in the appropriate fields, and they are
correct, the information is processed and the Access
Descriptor Display window appears. At this point you
are able to select the items you wish to appear when
creating a view descriptor.
Multi-User
specifies the execution environment.
DB2
CREATING A VIEW DESCRIPTOR
Use the View Descriptor Display \Vindow to define,
edit, or browse a view descriptor. You use this window
to select items for a view descriptor and to choose SAS
variable names, formats, informats, and lengths if Ute
access descriptor has not assigned them with Assign
Names ~ YES.
Authorization Id
taken from access descriptor.
cannot be edited.
This field
Table Name
taken from access descriptor.
cannot be edited.
This field
SSlD
taken from access descriptor.
cannot be edited.
The following fields are common in the interface
software for the database management systems.
This field
SQljDS
Library
specify the libref associated with the SAS data
library where you want to store the view
descriptor.
Authorization 10
taken from access descriptor.
cannot be edited.
584
This field
Table Name
taken from access descriptor.
cannot be edited.
DBMS data in SAS procedures and the DATA step in
virtually the same way you use SAS data files. You can
also select and combine data described by view
descriptors (from other DBMS) using the SAS
WHERE statement and the SQL procedure. You
cannot updata your DBMS data directly using the
DATA step. but you can update a DBMS data using
the following procedures: APPEND, FSEDIT,
FSVI EW, and SQ L.
This field
ORACLE
Table
taken from access descriptor.
cannot-be edited.
User
Name
taken from access descriptor.
cannol be edited.
This field
The following are some differences found in the
SAS/ACCESS interface Software:
This field
DB2,ORACLE
Rdb,IYMS
Database
taken from access descriptor.
cannol be edited.
This field
.Table Name
taken from access descriptor.
cannot be edited.
This field
Any ORDER BY clause associated with the view
descriptor is ignored by the FSEDIT procedure.
The data are not presented for editing in any
particular order .
DB2, SQL/DS, ORACLE, and RdbjVMS
In SAS/FSP procedures. scro1ling backward
through data described by a view descriptor is less
efficient than a SAS data file because the DBMS'
cursors process rows first-to-Iast only, not last-tofirst. For example. suppose the table has 5.000
rows and the current row is 3,400. To scroll
backward to row 3,399, PROC FSEDIT must
sequentially pass rows 1 through 3.398.
Prime INFORMATION
File
Name
taken from access descriptor.
cannot be edited.
This field
Vocabulary Path
taken from access descriptor.
cannot be edited.
This field
Prime INFORMATION
You cannot update Prime INFORMATION data
through the SASjACCESS Interface.
Once the fields are filled correctly and the items are
selected for your view descriptor? you have another
option. The SUBSET command displays the Selection
Criteria Entry Window. Use this window to specify
criteria for selecting logical entries to be presented to
the SAS System and to specify a sort order for the data.
The SAS System sends the criteria you enter to your
database management software to be processed when
you use the view descriptor.
CREATING AND LOADING YOUR DATABASE
The DBLOAD procedure enables you to create and
load a database from a SAS data file or data described
from a view descriptor. The following fields are
common .in the interface software of the database
management systems:
Note: The SUBSET command is not available in the
SAS/ACCESS interface to Prime INFORMATION.
Input Data
specifies the name of the input SAS data set. If
you do not enter a value. the default is the last
data set that was created.
USING YOUR DBMS DATA IN SAS PROGRAMS
Once the descriptors are created you can begin to use
them in your SAS programs. The advantage of the
SAS/ACCESS interface to your DBMS is that it
enables the SAS System to read and write your 0 BMS
data directly from SAS programs. You can use your
Access Descriptor
specifies the name of the access descriptor to be
created when the procedure creates the new
585
database.
Authorization ID
specifies the authorization 10 for the new
table. If you do not enter a value. it defaults
to your userid.
The following fields vary based on the database
management system being accessed:
SYSTEM 2000 Dala Management Software
Table Name
specifies the name of the new table. You
must fill in this field because there is no
default value.
Database View
specifies the name of the view descriptor you
want to create. based on the new database.
The view descriptor name must not already
exist. This field is optional.
ssm
specifies the DB2 subsystem 10. You must
fill in this field because there is no default.
Password
specifies the password that will become the
master password for the new database.
When you enter the password. it does not
appear on the screen.
In Oatabase;Tablespace
specifies the name of the table space in which
you want the new table stored.
Commit Frequency
specifies the number of inserts you want
issued before a commit is done. An entry of
o indicates you want only one commit
performed after all inserts have been issued.
The default value is 1000.
Database Name
specifies the name of the new database. This
field must not be blank.
Multi-User
specifies the access mode. The default (NO)
indicates a database will be created in a
single-user environment. YES indicates a
Multi-User environment.
Error Limit
specifies the number of SQL errors you will
allow without stopping the load. The default
value is 100.
Label
specifies whether you want to use the SAS
label information for item names (yES).
The default is NO. which uses the
8-character SAS variable identifers for item
names. This field is only used when creating
a new database.
SQLJDS
Same fields specified as in D B2 software. In
SQLJDS Ibe term In DBSPACE is used in place of
In Database,rrablespace.
ORACLE
Create only
specifies whether you want to load any data.
YES means you want to create a new
database but you do not want to load any
data. NO (the default) means you do want
to load data.
Input Limit
the
maximum
number
of
specifies
observations you want to load into the
ORACLE table. A value of 0 indicates you
want to load all observations. The default
value is 5000.
DB2
User
Input Limit
specifies
the
maximum
number
of
observations you want to load into the DB2
table. A value of 0 indicates you want to
load all observations. The default value is
5000.
Name
specifies the ORACLE username.
If
usemame and password are left blank.
ORACLE's automatic operating system
OPS$sysid option is used.
Password
specifies the ORACLE password.
586
Table Name
specifies the name of the new table. You
must filJ in this field because there is nO
default value.
default value is 100.
Prime INFORMATION
Thc
SASjACCESS
interface
to
Prime
INFORMATION does not contain a DBLOAD
procedure.
SPACE
specifies the name of the ORACLE space
definition where you want the new table
stored.
Once the information has been processed from the
Load Identification Window. you proceed to the Load
Display Window. If you want to load a subset of your
input data, you can do so from this window. The
following are the common fields that exist in the
DBMS.
Commit Frequency
specifies the number of inserts you want
issued before a commit is done. An entry of
o indicates you want only one commit
performed after all inserts have been issued.
The default value is 1000.
Func
Error Limit
specifies the number of SQL errors you will
allow without stopping the load. The default
value is 100.
enables you to control whether a SAS variable
is loaded into the table (database). D drops a
column (item) from the load. S selects a
previously dropped column {item) with default
settings.
Column (Component) Name
lists all column (component) names for the new
table (database). The names default to the SAS
variable names. but you can change them.
Input Limit
maximum
number
of
specifies
the
observations you want to load into the
RdbjVMS table. A value of 0 indicates you
want to load all observations. The default
value is 5000.
Column Type
lists the data types for each column The values
are based on the SAS variable formats, but you
can change them. This field is not specified in
the SASjACCESS interface to SYSTEM 2000
Data Management Software.
Database
is the name and physical location of the
database in which you want the new table
stored. If you do not fill in this field, the
table is created in the default database, if you
have designated one.
Nulls
indicates whether the column accepts null
values. The default value is Y. but you can
change it. This field is not specified in the
SASjACCESS interface to SYSTEM 2000 Data
Management Software.
Table
specifies the name of the new table to be
created and loaded. You must fill in this
field because there is no default value.
SAS Name
lists the SAS variable names from the input data
set. You cannot edit this field.
Commit Frequency
specifies the number of inserts you want
issued before a commit is done. An entry of
o indicates you want only one commit
performed after all rows have been inserted.
The default value is 1000.
(SAS) Format
lists the SAS variable formats from the input
data set. You cannot edit this field.
The foUowing fields vary based on the database
management system being accessed:
Error Limit
specifies the number of VAX SQL errors you
will allow without stopping the load. The
587
SYSTEM 2000 Data Management Software
Space
is filted in with the space definition name
specified on the Load Identification Window.
You may edit this field.
Database
is filled in with the database name that was
specified in the Load Identification Window.
RdbjVMS
Lvi
is the level number for the SYSTEM 2000
item. The default value is 0, but you can
change it. The level number must he an
integer from 0 through 9.
Database
is filled in with the database name and
location specified in the Load Identification
Window. You may edit this field.
Index
allows you to specify the item as a key
If you type in the character Y in this
the item will become a key (indexed)
any other character or a blank means
key_The default is non-key.
item ..
field,
item;
non-
Table
is fiUed in with the table name specified in
the Load Identification Window. You may
edit this field.
Althougb the main purpose of the DBLOAD
procedure is to create and load your table (database),
there are other options.
DB2
Table
SYSTEM 2000 Data Management Software
is filled in with the table name that was
specified in the Load Identification Window.
You may edit this field.
To add data to an existing database, you must
issue the VIEWDESC= statement. If you are
adding new logical entries to the database, you can
specify the S2KLOAD statement, which causes the
procedure to use optimized load processing.
Database/Tablespace
is filled in with the database or table space
name specified in the Load Identification
Window. You may edit this field.
When creating a new database, the procedure
always creates an access and view descriptor.
SQLjDS
Table
is filled in with the table name that was
specified in the Load Identification Window.
You may edit this field.
The DBLOAD procedure allows you to have
records at multiple levels, but they must be on the
same path. If you have disjoint. schema records,
you must create the database definition outside of
the DBLOAD procedure.
DBSPACE
is filled in with the database or table space
name specified in the Load Identification
Window. You may edit this field.
The following applies to DB2. SQLjDS. ORACLE and
RdbjVMS:
You can use the procedure to submit SQL
statements without creating and loading a table.
The Query Entry Window can be invoked from
either the Load Identification Window or the Load
Display Window. The SQL statements you enter
must not refer to the table being created because it
does not exist. Otherwise, you can enter any valid
SQL statement except the SELECT statement.
(However. you can enter the SELECT statement as
a substatement within another statement. If you
have stored your SQL statements in an external
file. you can use the INCLUDE command to copy
ORACLE
User
Name
is filled in with the ORACLE user name that
was specified in the Load Identification
Window. This field cannot be modified.
Table Name
is filled in with the table name specified on
the Load Identifi~ation Window. You may
edit this field.
588
them to the window.
CONCLUSION
The Multiple Engine Architecture's main purpose was
to access data stored in a database management system
QUEST PROCEDURE
through a transparent method. The naming convention
The QUEST procedure is the fourth part of the
SASjACCESS interface to SYSTEM 2000 Data
Management Software. The QUEST procedure allows
you to access a SYSTEM 2000 database directly, that
is. without using a view descriptor. The procedure is
basically a messenger for SYSTEM 2000 statements:
when you submit a statement in the QUEST procedure,
the SAS System scans the statement and passes it to
SYSTEM 2000 software. which then executes iL
SYSTEM 2000 software includes an interactive
language. also called QUEST. that is used for creating.
browsing, updating, and managing SYSTEM 2000
databases. The QUEST procedure gives you full access
to that language, either from the display manager.
interactive line-mode sessions, or balch mode. This
procedure enables you to access SYSTEM 2000
software to perform a variety of tasks, for example.
and the design of the SASjACCESS interface software
was kept very similar, if not the same, across the
different DBMS vendors. Through the ACCESS
procedure you can create -descriptors to access your
data. Data that can be stored in hierarchical or
relational databases. The data may be handled
differently based on the DBMS used. but when that
data is used with your SAS procedures, the result is the
same. The DBLOAD procedure enables you to create
and load tables (databases) from your existing SAS
data files. Most businesses have more than one DBMS
installed, and that is why it is so important to keep the
terminology similiar. And by using the SASjACCESS
interface software, you can now generate reports from
different DBMS through the SAS System.
SAS, SASjACCESS, SASjFSP, and SYSTEM 2000 are
registered trademarks and Multi-User is a trademark of
SAS Institute Inc., Cary, NC, USA.
* retrieving data from a database
* updating data in a database
* defining a new database
* assigning passwords to a database
* saving a database
IBM is a registered trademark and DB2 and SQLjDS
are trademarks of International Business Machines
Corporation.
* restoring a database
* enabling rollback.
RdbjVMS, VAX, and VMS are trademarks of Digital
Equipment Corporation.
PRIMOS is a registered trademark and Prime
INFORMATION is a trademark of Prime Computer,
Inc.
ORACLE is
Corporation.
589
a
registered
trademark
of Oracle