Getting Started with SAS/SHARE

Frequently Asked Questions (FAQs) about SAS/SHARE

General Questions

What is SAS/SHARE software? Why would I use it?

You use SAS/SHARE software in the following situations

More than one user needs to update a SAS file (or several SAS files) at the same time.
Users want to access SAS files on a server without having to use a separate SAS/CONNECT remote login for each user.

Where can I read about SAS/SHARE software?

You can read about SAS/SHARE in the following documents:

This document, which explains SAS/SHARE software, describes the parts of the software, and applies to all operating environments. It also includes basic and detailed reference material for PROC SERVER, PROC OPERATE, the LIBNAME statement, and the LOCK statement.
Also see Communications Access Methods for SAS/CONNECT and SAS/SHARE for information about using a communications access method to connect from a client session to a server session and for instructions to configure the access method.

Do people have to use a new SAS procedure to share their data?

No. The users who add and maintain data continue to use the SAS procedures and windows that they already know: PROC FSEDIT, PROC APPEND, PROC FSVIEW, and so on.

Instead of requiring users to change the SAS tools they already know and use, SAS/SHARE takes advantage of the SAS Multiple Engine Architecture (MEA) to allow those SAS tools to access data through a "traffic cop" that is formally known as a SAS/SHARE server. A SAS/SHARE server allows many users to read and update data concurrently in one or multiple SAS files by tracking locks on observations, catalog entries, and SAS files.

Does each person responsible for maintaining data have to run an individual SAS/SHARE server?

No. There are three roles that users assume with respect to SAS/SHARE:

End user: reads, adds, and updates data.
Applications developer: writes SAS programs used by the end users.
Server administrator: makes sure SAS/SHARE servers are available to the end users.

The three roles can be performed by the same person, or one person might perform two roles, or each role might be assigned to a separate group of people.

It's not unusual for the same person to perform the tasks of an applications developer and a server administrator, for example, when the person who develops an application is responsible for the SAS/SHARE server or servers used by that application.

Three people? I hope this software doesn't require the effort of a large team of people.

No, three roles. The three roles help organize the efforts so that shared maintenance of data is possible. In real life, the responsibilities of the various people involved in a project might overlap. Often, the same person who develops an application also maintains a SAS/SHARE server.

To help you keep track of how responsibilities usually are divided when multiple users need to update a SAS file at the same time, the remainder of this section answers the questions most frequently asked by end users, application developers, and server administrators.

FAQs by End Users

How do I get started with SAS/SHARE?

You use an application that someone else developed to read, add, or update data in one or in multiple SAS files. Occasionally, you find that an observation, a catalog entry, a file, or a library is locked by another user. If that happens, a message appears and you cannot modify the data. SAS/SHARE keeps track of which users have which data locked, so users cannot cause each other's changes to become mysteriously "lost."

How can I find out if I'm accessing a SAS library through a SAS/SHARE server?

The SERVER= option is required in a LIBNAME statement (or, in SCL programs, any LIBNAME() function) for a library to be accessed through a SAS/SHARE server.

When a library is accessed through a server, the information that is displayed in the Log window about the LIBNAME statement shows you that the engine that was used to access the library is named REMOTE, and the physical name is a subdirectory accessed by the server SAS session.

Use the LIST option in a LIBNAME statement to obtain information about how a SAS library is defined to a SAS session. This information includes the following:

the name of the server through which the library is accessed.
the libref used by the server to refer to the library. (This libref might be the same as or different from the user's libref for that library.)
the engine used in the server SAS session to read and write files in the library.
the operating environment and machine type on which the server is running.

FAQs by Applications Developers

How do I get started with SAS/SHARE?

See SAS/SHARE: Learning to Use.

Topics of importance for applications developers include SAS library access, locking data objects, and SAS programming considerations. See Writing End-User Applications to Access Shared Data. For a sample SCL application, see SAS Component Language (SCL) Application. For complete details about locking, see Locking SAS Data Objects.

You might also find helpful information about how server administrators manage SAS/SHARE servers. See Managing a SAS/SHARE Server (Server Administrators). For specific details about creating a SAS/SHARE server and setting SAS options to enhance performance and to establish logging parameters, by operating environment, see Creating the SAS/SHARE Server Environment.

What do I have to do to a SAS library so that users can access it through a SAS/SHARE server?

You have to add a SERVER= option to each LIBNAME statement that a user will use to access the library.

You might want to predefine one or more libraries to a server. Include a LIBNAME statement for each library before executing the PROC SERVER statement. Including a LIBNAME statement removes the requirement for a physical name in each user's LIBNAME statement that accesses any of those libraries. This can make it easier to maintain your application.

For more information about server libraries, see Managing a SAS/SHARE Server (Server Administrators). For details about the LIBNAME statement, see Remote Library Services.

Can a SAS/SHARE server access a SAS library across a network?

Yes, but you usually do not want to organize it that way.

Even though a SAS/SHARE server is not exactly like other file servers that you might be familiar with, it is still a process that generates a lot of disk I/O because a server generates I/O to files on behalf of a large number of users. Therefore, you want the path length between the server SAS session and the physical disk to be as short as possible. Try to store data on the same computer as the server that is used to access that data, whenever possible.

I've used servers before. A SAS/SHARE server is similar to the file servers we have on our network, isn't it?

Not really. Usually, file servers are not aware of the content of the files they manage, but a SAS/SHARE server allows several users to update the same copy of a SAS file at the same time.

SAS/SHARE is tuned to manage locking conflicts within SAS files, such as two users attempting to update the same observation of a SAS data file or two users attempting to modify the same entry in a SAS catalog. SAS/SHARE is not optimized to provide the bulk data transfer services at which many file servers excel.

Can a server use more than one communications access method?

Yes. A server administrator uses SAS options to enable this.

If your application requires the use of more than one communications access method, ask your server administrator to set up the server for your application with the access methods that you need. For more information about access methods, see Specifying a Communications Access Method.

Do I have to use a different SAS/SHARE server for each file that is updated by the users of my application?

No. A server can share many files in the same SAS library and in many different SAS libraries at the same time.

Is there a limit on how many users or libraries a SAS/SHARE server can support?

No. There are no limits coded into the software, and you do not need to use SAS options to specify how many users or files a server will support at one time.

However, a server is the same as any other process on a computer; as it is asked to handle greater workloads it takes longer to do the work. It is possible to put so much traffic through a server that users complain about response time. If any of your servers become that busy, you should consider creating one or more additional servers and dividing the files among the servers.

See your server administrator about creating additional servers.

Do I need to ask my server administrator to start and stop my application's server each day?

Probably not. As with other processes on a computer, SAS/SHARE servers can usually run for long periods of time without intervention. Sometimes periodic maintenance or backup activity requires processes to be stopped for a period of time and then restarted. Servers are not immune to such interruptions.

FAQs by Server Administrators

How do I get started with SAS/SHARE software?

Read Getting Started with SAS/SHARE, giving special attention to when PROC SERVER is started and stopped. Occasionally, you might need to use PROC OPERATE, so you should read those tasks in this exercise.

Usually, a SAS/SHARE server is started when initialization of the operating environment is completed, and it continues to run until the computer is shut down or the server is terminated. You should be familiar with creating and managing those types of processes. Of course, a server only generates I/O or uses the processor while users are accessing data through it; a server doesn't process a residual amount of work when it is not processing work on behalf of other users.

Because a server executes within a SAS session, you need to know how to invoke SAS on each computer on which a server will run.

I've used servers before. A SAS/SHARE server is similar to the file servers we have on our network, isn't it?

Not really. Ordinarily, file servers are not aware of the content of the files they manage, but a SAS/SHARE server allows several users to update a single copy of a SAS file at the same time. Also, SAS/SHARE servers automatically translate transmitted data when the client operating environment represents data differently from the server operating environment.

Is being a SAS/SHARE server administrator a full-time job?

No! SAS/SHARE is designed to require no regular maintenance or other administrative activity.

Can a server administrator control access to a server?

Yes. By default, SAS/SHARE does not restrict who can connect to a server or which files they can access, but you can restrict access to a server with the OAPW= and UAPW= options in the PROC SERVER statement. The OAPW= option specifies a password, which the server administrator must supply (in the OPERATE procedure), to connect to the server. The UAPW= option specifies a password that the user must supply in the LIBNAME statement to connect to the server. Of course, your file system restricts a server's access to files based on the access permission set for the files and the server's process. You can also set up a secured server. For more information, see Server Security.

Can a server administrator control which libraries users can access through a server?

Yes. For each server, you can prevent users from defining libraries to the server and restrict them to using only those libraries that you define. To do this, use the NOALLOC option in the PROC SERVER statement. See Limiting the Libraries a Server Can Access.

Remember that passwords can be used to restrict access to individual SAS files. See the PW= data set option in SAS Language Reference: Dictionary for more information about data set passwords.

How can I terminate a user's connection to a SAS/SHARE server?

First, decide whether you want the access terminated immediately or as soon as it is convenient for the user.

The QUIESCE USER command disconnects a user from a server when the user ends the SAS program step currently being executed or closes the window currently being used. The STOP USER command immediately terminates a user's connection to a server and might cause loss of updates that have not been communicated to the server.

In either instance, the user cannot reconnect to the server until a START USER command is executed, which lets the user reconnect, or until the server is restarted. Servers do not retain a list of stopped users when they are terminated and restarted.

See Quiescing User Access to a Server and Terminating User Connections to a Server.

How can I stop a SAS/SHARE server?

The QUIESCE SERVER command causes a server to stop when all users have disconnected from the server. The STOP SERVER command immediately stops the server and might cause loss of updates that have not been communicated to the server.

See Quiescing a Server and Stopping a Server.

Can a server use more than one communications access method?

Yes, if your operating environment supports more than one communications access method. See Specifying a Communications Access Method for information about the communications access methods available on your operating environment.

How can I determine when I need to create a second SAS/SHARE server?

You need to create a second server when the traffic on a server becomes so heavy that an application's performance is less efficient.

Just as you periodically check the resource consumption of the other service processes on a computer, you should, from time-to-time, consider the amount of CPU, I/O, and virtual storage the servers are using. Using operating environment management tools, you might notice that a server is executing a very large number of disk I/O operations or needs a very high percentage of the processor. When you observe those conditions, consider moving some of the work from that server to another, possibly new, server.

Distributing the workload among servers must be a cooperative effort between server administrators and applications developers. SAS provides a set of autocall macros that assign resources to servers symbolically. These macros can make moving resources from one server to another much easier. See SAS/SHARE Macros for Server Access.

Accessibility Features in SAS Products

For information about accessibility for any of the products mentioned in this book, see the documentation for that product. If you have questions or concerns about the accessibility of SAS products, send e-mail to accessibility@sas.com.

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