TweetFollow Us on Twitter

dtF
Volume Number:10
Issue Number:9
Column Tag:Tools of the Trade

dtF

A royalty-free relational database management system

By Jeff Fisher, SalesKit Software Corp.

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

About the Author

Jeff Fisher - Jeff works at SalesKit Software Corp. While looking around for a good database to use with their application software, they ran across dtF. Skeptical at first, he checked it out. Now he’s uses it and loves it. Apparently he’s not alone in how he feels about it. His former partner liked it so much he became the US distributor for it (dtF Americas).

Finally there’s a royalty-free relational database management system for Macintosh C/C++ application developers. The performance may surprise you, yet the library is small and requires only a few hundred K of RAM at runtime. It features SQL, full transaction control, error recovery, client server architecture and is optimized for the Macintosh. The new product is call dtF and was developed in Germany. Like German automobiles, dtF is well built and efficient in every aspect. Unlike German automobiles, dtF does not cost an arm and a leg.

Performance

Many SQL database management systems are just an SQL interface plopped on top of an ISAM record access system. Such a system can’t deliver the performance of a system designed from the ground up. dtF is a true set-oriented SQL engine designed specifically for optimum performance on personal computer architectures.

The performance of dtF is unequaled in our tests. We have clients who want to access large databases (>22,000 records) from a standalone version of our software. With our old database engine, queries that took more than five minutes now take less than thirteen seconds with dtF! I always hate performance comparisons because they never compare aspects relevant to my projects. There is really no substitute for doing your own tests. We compared dtF’s data access speed with 4D, Oracle, Inside Out, and FoxPro 2.5. We found dtF to be over eight times faster on multi-table ordered queries (an aspect relevant to our project) than the nearest competitor.

Client/Server

dtF implements a client/server architecture. It does not use file sharing to support multi-user table access over the network. The dtF server processes queries and sends only results to the client. This ensures high performance, efficient use of the network bandwidth, and data security. File sharing approaches place high demands on a network and the onus of doing lock management, deadlock detection, and error recovery on the application developer.

One interesting aspect of dtF is how it divides labor between client and server. Many client server systems assume a “dumb” client. This traditional approach creates a bottleneck at the server - not only does the server perform client requests but each time a user scrolls a list window the client must ask the server to send down more data. This can create a lot of unwanted network traffic as well as bog the server down with intermittent requests for data. The dtF server passes results to the client so no network traffic is generated when accessing results. This approach is ideal for modern network environments and puts your existing equipment to good use. The precious power of the server is reserved for processing transactions and the client can get right to the job of displaying results.

Both single-user standalone and client-server versions of dtF use the same client-server model and interface.

Stand alone applications with dtF can be converted to multi user client/server applications by simply adding three library calls to your code. This helps dtF offer a practical standalone interface, perhaps the only one for a Macintosh SQL DBMS.

Transaction Control

dtF supports true transaction processing. This is the only way to ensure data integrity. Consider an order processing application that requires one transaction to add the order and five more transactions to add line items to another table. If there is a network failure on the third line item, it is essential to abort the entire transaction. In such a case dtF would simply rollback the transactions and return the database to a state which looks like they never took place.

The current Macintosh version of dtF server can handle 63 parallel concurrent transactions with automatic lock management, automatic deadlock detection, and error recovery. With an ISAM record access system, you have to explicitly lock records and indexes when performing updates and deletes. Lock management and deadlock avoidance can become very complex when you have multiple related tables. For example:


/* 1 */
// must lock both tables to avoid deadlock

act_locked = bogus_lock(accounts);
cnt_locked = bogus_lock(contacts);

if (!act_locked || !cnt_locked )
 return errorDeadLocked;

bogus_use(accounts); // use the accounts table
if (bogus_seek (theAccountID))//  find the desired record
{
 bogus_delete(); // delete the account record
 bogus_use(contacts);// use the contacts table
 bogus_settag(“act_id”);
 if (bogus_seek (theAccountID))  //  find the desired record
 {
 bogus_delete(); // delete the account record
 }
}
bogus_unlock(accounts);
bogus_unlock(contacts);

On the other hand, all lock management and deadlock detection is done by dtF. Client/server applications require no special multiuser considerations. You don’t have to write anything similar to the above code.

Security

All data within a dtF database is encrypted and compressed. Tables requiring 22MB in another database management system took less than 4MB in dtF. Data encryption ensures that data cannot be pilfered, even with disk editors. Access rights are granted at the table level. Read, update, insert, and delete privileges can be set at the table level. Administration rights (create and delete tables and indexes) are also granted at the table level.

Utilities

dtF comes with a database administration tool and browser (written with MacApp) call dtFQuery.

You can use dtFQuery to:

• Import data

• Export data

• Issue SQL statements.

• Create databases with your own creators and file types

• Repair corrupted database files.

Compatibility

dtF supports a large subset of ISO standard SQL, and it is optimized for performance and ease of use on the Macintosh. dtF libraries are included for the latest MPW C/C++ and Symantec environments. I use dtF with MacApp 3.0.1 and TCL and have included a sample MacApp application [available on this month’s source disk and the online services - Ed stb].

API

Both the multi user and stand alone versions of dtF have the same C interface. This allows you to develop applications with client server architecture that will perform great in single user, single platform situations. Converting a single user applications using dtF into a multi user application is easy. Add three function calls to select a dtF server and relink with the multiuser object library.

There are two interface levels called simply Level 1 and Level 2. This provides the developer with two possible levels of abstraction and encapsulation. The Level 2 interface is a high-level, easy-to-use interface. The Level 1 interface gives you raw access to dtF. We use the high-level interface for all of our testing and development and have found no need to access the low level interface so far.

In our MacApp 3.0.1 application, we call 15 different dtF functions. A fully functional application could use as few as three: select database (or server), logon, and execute. While this seems almost too simple, remember that all operations are encapsulated in the SQL you submit to the server.

All memory used by dtF is allocated at startup, so you won’t have to struggle with intermittent low-memory conditions caused by the DBMS. And because it has its own virtual memory and caching system, you will never have to preflight queries. The virtual memory and caching systems can be optimized by adjusting values in a resource.

dtF is ideal for use with MacApp because it will not interfere with MacApp memory allocation and segment management schemes. Other database management systems require you to jump through a few hoops to fit in with MacApp. dtF requires no explicit call to initialize or shutdown, and you don’t have to provide idle handlers to dtF.

Why SQL?

An SQL database management system like dtF offers the developer a single interface for data definition, data manipulation and data administration. ISAM (Indexed Sequential Access Method) architectures aren’t as convenient for getting at your data (selecting indexes, filtering unwanted records, etc ). With an SQL database management system, you describe the results you want with the SQL statement and the database engine does the rest.

As an example, suppose that you are developing a contact management system and you want a list of the contacts with last name equal to “Smith” grouped by account name. The code required to retrieve the desired result from dtF is shown below.


/* 2 */
char theSQL[255];

strcpy(theSQL, "select * from accounts,contacts where
 accounts.act_id = contact.act_id and 
 contacts.l_name = 'Smith' group by
 account.act_name order by contacts.zipcode");

dtF2exec(theSQL);

   // now access the results which are already sorted

All you have to do is submit a simple SQL statement and dtF does all the processing.

The same query with a typical ISAM record access system would look something like the following.


/* 3 */
bogus_use(accounts); // use the accounts table
bogus_settag(“act_name”);
actRecNum = bogus_recordcount();

for (act_index = 1; act_index <= actRecNum; ++act_index)
{
 bogus_fieldstring(“act_name”,accountName);
 bogus_fieldstring(“act_id”,accountID);

 bogus_use(contacts);
 bogus_settag(“l_name”);
 cntRecNum = bogus_recordcount();

 bogus_seek (“Smith”)
 do     // look for hits
 {
 bogus_fieldstring(“act_id”,cntAccountID);
 if (strcmp(cntAccountID,accountID) == 0) // if account ids match
 {
 // we finally found one
 }
 }while (bogus_skip(1));

 bogus_use(accounts);
 bogus_settag(“act_name”);
 bogus_skip(1);
}

Or even worse.


/* 4 */
bogus_act_ref = bogus_open(accounts);// use the accounts table
bogus_cnt_ref = bogus_open(contacts);// use the contacts table

bogus_setbuffer(bogus_act_ref ,&bogus_act_struct); 
 // <<hardcoded structs
bogus_setbuffer(bogus_cnt_ref ,&bogus_cnt_struct); 
 // <<hardcoded structs

bogus_setkey(bogus_act_ref ,”act_name”);
bogus_setkey(bogus_act_ref ,”l_name”);

while (bogus_posvalid(bogus_ref,&bogus_struct))
{
 bogus_cnt_hardcodestruct.act_id = bogus_act_struct.act_id;
 
 // use up a bunch of memory building a result set

 bogus_do_find(bogus_cnt_ref,&bogus_cnt_struct)
 tempSet = bogus_build_set(bogus_cnt_ref ,bogus_cnt_struct);
 bogus_set_read(bogus_cnt_ref ,tempSet );
 bogus_sort_set(tempSet );

 // intersect result set with previous result sets
 bogus_intersection(resultSet,tempSet);
 bogus_skip(bogus_cnt_ref ,1);
}
   // finally use the result set to access selected records

This seems like an extreme example, but I’ve used a database engine that even required me to check to see if the current record was marked as deleted before using the result.

Cursors

When you are going to deal with queries which will generate very large results, sometimes it’s better to let the server keep track of the results, and then use a set of “cursor” calls to navigate through the results without needing to bring them all into the client’s memory all at once. A cursor is a reference into the results, and it can be used to index through the results. Developers familiar with DAL, ODBC, Oracle call interface, Sybase DBLib or any other SQL C programming interface are probably already familiar with this concept.

For an example, consider the large database that MacTech Magazine uses to keep track of its subscribers. The subscription guy needs to notify individuals who’s subscriptions will run out soon to help prevent them from missing a single excellent MacTech issue. He needs a subset of the total subscribers and he may also want them ordered by zip code (so he can save some money on postage). A cursor is an efficient way of producing the ordered subset without building a table in the client’s memory.

In a graphical operating system like the Macintosh, you may want several cursors, one for each list view or one for each window. For example, in a contact management application, you have a list of all available contacts ordered by last name. In another window, you might have a list of contacts with whom you have an appointment, ordered by appointment date. There could be thousands of contacts (my boss has over 6000 in his contact manager) and the query results might just be too big to hold in memory. If every window has its own cursor, each window can display different result sets from the appointments table at the same time. This is supported by a dtF concept called workspaces. Each cursor is referenced by a unique workspace identifier.

dtF allows forward and backward cursor movement. Some client server systems will only move forward or require you to build a result buffer in memory to move backward. Bi-directional cursor movement can really simplify your application.

Support

After using several different DBMS systems, we have amassed many support horror stories and were very concerned about using a database developed in Germany. We decided go to Germany and get the story first hand. dtF was developed by the Theta Group and I was very pleased to find out that they are true Macintosh fanatics. We have been developing with dtF for almost six months and have been thrilled with the support we have received. While all support is currently provided by the Theta Group, plans are well underway to provide support in the United States through dtF Americas, the new US distributor of dtF.

Future of dtF

Currently in the works are a multi user version using TCP/IP rather than AppleTalk, further performance optimization, and cross-platform support. An AppleScript extension using dtF is already available from Graphical Business Interfaces and many other third parties tools and applications will be available in the US by the printing of this article.

Conclusion

dtF is a relational database management system created by Macintosh developers for Macintosh developers. Efficient. Fast. SQL. Compact. Safe. We have examined all of the options and have chosen dtF and now you know why.

Pricing information: dtF Evaluation $129, dtF Macintosh SDK $695, dtf LAN Macintosh SDK $1595, dtf Server $1295.

For more information, contact dtF Americas, Inc. at 14720 Plumas Drive, Chesterfield, MO 63017. (800) DTF-1790 voice, (314) 530-1697 fax, AppleLink DTF.AMERICA.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Printopia 3.0.4 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
Tinderbox 7.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
ExpanDrive 6.1.6 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
VOX 3.0.1 - Music player that supports m...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
Merlin Project 4.3.3 - $289.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more
Mac DVDRipper Pro 7.1 - Copy, backup, an...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
iMazing 2.5.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Pinegrow 4 - Mockup and design webpages...
Pinegrow (was Pinegrow Web Designer) is desktop app that lets you mockup and design webpages faster with multi-page editing, CSS and LESS styling, and smart components for Bootstrap, Foundation,... Read more
iExplorer 4.1.11 - View and transfer fil...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
Merlin Project 4.3.3 - $289.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more

Latest Forum Discussions

See All

The best Black Friday mobile game deals
Black Friday's upon us, and if you've happened to nab a fancy new phone during the week's big savings, you might be searching for some new games to fill up space on your new gadget. There are a lot of great games on sale right now for Black Friday... | Read more »
The best mobile games to play while your...
Thanksgiving is a time to reconnect with loved ones, eat lots of food, and all of that jazz, but once the festivities start to wind down, folks tend to head to the couch to watch whatever football is happening for Turkey Day. | Read more »
The best Black Friday deals for Apple ga...
Black Friday is hours away at this point, but many popular retailers are getting a jump on things with plenty of pre-Black Friday sales already available. Many of those early bird sales including some sharp discounts on the latest Apple phones... | Read more »
The Inner World 2 (Games)
The Inner World 2 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Solve mind-bending puzzles in a world full of mystery and save the family of the flute-noses! Their dynasty has been... | Read more »
warbot.io wants you for the robot wars
Fans of epic gundam-style battles will find a lot to love in warbot.io, the first game for up and coming developer Wondersquad. The game saw a lot of success when it first launched for browsers and Facebook, and now even more people are getting the... | Read more »
Uncover alien mysteries in cross-genre s...
If the Alien franchise taught us anything, it’s that landing on a strange planet at the behest of a faceless corporation is probably asking for trouble. And Eldritch Game’s Deliria doesn’t prove otherwise. In 2107, Dimension LG7 is rich with... | Read more »
The best mobile games to play during dre...
| Read more »
Animal Crossing: Pocket Camp beginner...
Animal Crossing: Pocket Camp, was just announced yesterday, but it's already in soft launch in Australia. No matter where you are in the world, you can still get access to the soft launch on iOS, so we've devised a few beginner tips for folks who... | Read more »
The mobile gamer's guide to Black F...
We're starting to catch wind of some exciting deals in the mobile gaming space for Black Friday. There are big discounts on mobile phones and accessories cropping up already, so you might want to get a move on things ahead of the big day. It's... | Read more »
The best pre-Black Friday deals - Novemb...
Black Friday will soon be upon us, but online retailers are already getting a headstart on the steep discounts. Don't wait until Friday—you'll find some pretty good deals all over the internet without waiting in lines or competing with other... | Read more »

Price Scanner via MacPrices.net

Black Friday 2017: Find the best deals and lo...
Scan our exclusive price trackers for the latest Black Friday 2017 sales & deals and the lowest prices available on Apple Macs, iPads, and gear from Apple’s authorized resellers. We update the... Read more
Black Friday: 27″ 3.4GHz iMac for $1599, save...
Amazon has the 27″ 3.4GHz Apple iMac on sale for $1599.99 as part of their Black Friday sale. That’s $200 off MSRP, and shipping is free. Their price is currently the lowest price available for this... Read more
Black Friday: 13″ 2.3GHz/256GB MacBook Pro fo...
Amazon has the 13″ 2.3GHz/256GB Apple MacBook Pro on sale for $1299.99 as part of their Black Friday sale. Shipping is free: – 13-inch 2.3GHz/256GB Space Gray MacBook Pro (MPXT2LL/A): $1299.99 $200... Read more
Black Friday: 15″ 2.9GHz MacBook Pros for $25...
Amazon has lowered prices on Silver and Gray 15″ 2.9GHz MacBook Pros to $2549.99. That’s $250 off MSRP, and shipping is free. Their prices are the lowest available for these models from any reseller... Read more
Lowest Black Friday prices on Apple MacBooks:...
Save $150-$420 on the purchase of a MacBook Pro, MacBook, or MacBook Air this Black Friday and Holiday weekend with Certified Refurbished models at Apple. In many cases, Apple’s refurbished prices... Read more
Black Friday: Apple Watch Series 1 for $70 of...
Macy’s has discounted Series 1 Apple Watches by $70 on their online store as part of their Black Friday sale: – 38mm Series 1 Apple Watch: $179, $70 off – 42mm Series 1 Apple Watch: $209, $70 off... Read more
Apple offers 2016 13-inch MacBook Airs, certi...
Apple has Certified Refurbished 2016 13″ MacBook Airs available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.6GHz/8GB/128GB MacBook Air: $... Read more
Black Friday sale: Mac minis for $100 off MSR...
B&H Photo has Mac minis on sale for up to $100 off MSRP as part of their Black Friday sale, each including free shipping plus NY & NJ sales tax only: – 1.4GHz Mac mini: $399 $100 off MSRP – 2... Read more
Use your Apple Education discount to save up...
Purchase a new Mac using Apple’s Education discount, and take up to $300 off MSRP. All teachers, students, and staff of any educational institution with a .edu email address qualify for the discount... Read more
Adorama posts Black Friday deals on Apple Mac...
Adorama has posted Black Friday sale prices on many Macs, with MacBooks and iMacs available for up to $200 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: MacBook Pros... Read more

Jobs Board

Business Development Manager, *Apple* Pay -...
# Business Development Manager, Apple Pay Job Number: 112919084 Santa Clara Valley, California, United States Posted: 18-Aug-2017 Weekly Hours: 40.00 **Job Summary** Read more
Digital Marketing Media Planner, *Apple* Se...
# Digital Marketing Media Planner, Apple Services Job Number: 113080212 Culver City, California, United States Posted: 03-Oct-2017 Weekly Hours: **Job Summary** Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Business Development Manager, *Apple* Pay -...
# Business Development Manager, Apple Pay Job Number: 112919084 Santa Clara Valley, California, United States Posted: 18-Aug-2017 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 56553863 North Wales, Pennsylvania, United States Posted: 17-Jun-2017 Weekly Hours: 40.00 **Job Summary** Are you passionate Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.