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

SketchUp 19.1.174 - Create 3D design con...
SketchUp is an easy-to-learn 3D modeling program that enables you to explore the world in 3D. With just a few simple tools, you can create 3D models of houses, sheds, decks, home additions,... Read more
ClamXav 3.0.12 - Virus checker based on...
ClamXav is a popular virus checker for OS X. Time to take control ClamXAV keeps threats at bay and puts you firmly in charge of your Mac’s security. Scan a specific file or your entire hard drive.... Read more
BetterTouchTool 3.151 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom)... Read more
FontExplorer X Pro 6.0.9 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more
Dropbox 77.4.131 - Cloud backup and sync...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keeps them up-to-date between systems... Read more
DiskCatalogMaker 7.5.3 - Catalog your di...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast Finder-like intuitive look and feel Super-fast search algorithm Can compress catalog data for... Read more
Notion 1.0.7 - A unified workspace for m...
Notion is the unified workspace for modern teams. Notion Features: Integration with Slack Documents Wikis Tasks Note: This application contains in-app and/or external module purchases. Version 1.0... Read more
Microsoft Office 2016 16.16.12 - Popular...
Microsoft Office 2016 - Unmistakably Office, designed for Mac. The new versions of Word, Excel, PowerPoint, Outlook, and OneNote provide the best of both worlds for Mac users - the familiar Office... Read more
Little Snitch 4.4.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
MainStage 3 3.4.3 - Live performance too...
Apple MainStage makes it easy to bring to the stage all the same instruments and effects that you love in your recording. Everything from the Sound Library and Smart Controls you're familiar with... Read more

Latest Forum Discussions

See All

Upcoming visual novel Arranged shines a...
If you’re in the market for a new type of visual novel designed to inform and make you think deeply about its subject matter, then Arranged by Kabuk Games could be exactly what you’re looking for. It’s a wholly unique take on marital traditions in... | Read more »
TEPPEN guide - The three best decks in T...
TEPPEN’s unique take on the collectible card game genre is exciting. It’s just over a week old, but that isn’t stopping lots of folks from speculating about the long-term viability of the game, as well as changes and additions that will happen over... | Read more »
Intergalactic puzzler Silly Memory serve...
Recently released matching puzzler Silly Memory is helping its fans with their intergalactic journeys this month with some very special offers on in-app purchases. In case you missed it, Silly Memory is the debut title of French based indie... | Read more »
TEPPEN guide - Tips and tricks for new p...
TEPPEN is a wild game that nobody asked for, but I’m sure glad it exists. Who would’ve thought that a CCG featuring Capcom characters could be so cool and weird? In case you’re not completely sure what TEPPEN is, make sure to check out our review... | Read more »
Dr. Mario World guide - Other games that...
We now live in a post-Dr. Mario World world, and I gotta say, things don’t feel too different. Nintendo continues to squirt out bad games on phones, causing all but the most stalwart fans of mobile games to question why they even bother... | Read more »
Strategy RPG Brown Dust introduces its b...
Epic turn-based RPG Brown Dust is set to turn 500 days old next week, and to celebrate, Neowiz has just unveiled its biggest and most exciting update yet, offering a host of new rewards, increased gacha rates, and a brand new feature that will... | Read more »
Dr. Mario World is yet another disappoin...
As soon as I booted up Dr. Mario World, I knew I wasn’t going to have fun with it. Nintendo’s record on phones thus far has been pretty spotty, with things trending downward as of late. [Read more] | Read more »
Retro Space Shooter P.3 is now available...
Shoot-em-ups tend to be a dime a dozen on the App Store, but every so often you come across one gem that aims to shake up the genre in a unique way. Developer Devjgame’s P.3 is the latest game seeking to do so this, working as a love letter to the... | Read more »
Void Tyrant guide - Guildins guide
I’ve still been putting a lot of time into Void Tyrant since it officially released last week, and it’s surprising how much stuff there is to uncover in such a simple-looking game. Just toray, I finished spending my Guildins on all available... | Read more »
Tactical RPG Brown Dust celebrates the s...
Neowiz is set to celebrate the summer by launching a 2-month long festival in its smash-hit RPG Brown Dust. The event kicks off today, and it’s divided into 4 parts, each of which will last two weeks. Brown Dust is all about collecting, upgrading,... | Read more »

Price Scanner via MacPrices.net

Clearance 12″ 1.2GHz MacBook on sale for $899...
Focus Camera has clearance 12″ 1.2GHz Space Gray MacBooks available for $899.99 shipped. That’s $400 off Apple’s original MSRP. Focus charges sales tax for NY & NJ residents only. Read more
Get a new 2019 13″ 2.4GHz 4-Core MacBook Pro...
B&H Photo has new 2019 13″ 2.4GHz MacBook Pros on sale for up to $150 off Apple’s MSRP. Overnight shipping is free to many addresses in the US: – 2019 13″ 2.4GHz/256GB 6-Core MacBook Pro Silver... Read more
AirPods with Wireless Charging Case now on sa...
Amazon has extended their Prime Day savings on Apple AirPods by offering AirPods with the Wireless Charging case for $169.99. That’s $30 off Apple’s MSRP, and it’s the cheapest price available for... Read more
New 2019 15″ MacBook Pros on sale for $200 of...
B&H Photo has the new 2019 15″ 6-Core and 8-Core MacBook Pros on sale for $200 off Apple’s MSRP. Overnight shipping is free to many addresses in the US: – 2019 15″ 2.6GHz 6-Core MacBook Pro Space... Read more
Amazon drops prices, now offers clearance 13″...
Amazon has new dropped prices on clearance 13″ 2.3GHz Dual-Core non-Touch Bar MacBook Pros by $200 off Apple’s original MSRP, with prices now available starting at $1099. Shipping is free. Be sure to... Read more
2018 15″ MacBook Pros now on sale for $500 of...
Amazon has dropped prices on select clearance 2018 15″ 6-Core MacBook Pros to $500 off Apple’s original MSRP. Prices now start at $1899 shipped: – 2018 15″ 2.2GHz Touch Bar MacBook Pro Silver: $1899.... Read more
Price drop! Clearance 12″ 1.2GHz Silver MacBo...
Amazon has dropped their price on the recently-discontinued 12″ 1.2GHz Silver MacBook to $849.99 shipped. That’s $450 off Apple’s original MSRP for this model, and it’s the cheapest price available... Read more
Apple’s 21″ 3.0GHz 4K iMac drops to only $936...
Abt Electronics has dropped their price on clearance, previous-generation 21″ 3.0GHz 4K iMacs to only $936 shipped. That’s $363 off Apple’s original MSRP, and it’s the cheapest price we’ve seen so... Read more
Amazon’s Prime Day savings on Apple 11″ iPad...
Amazon has new 2018 Apple 11″ iPad Pros in stock today and on sale for up to $250 off Apple’s MSRP as part of their Prime Day sale (but Prime membership is NOT required for these savings). These are... Read more
Prime Day Apple iPhone deal: $100 off all iPh...
Boost Mobile is offering Apple’s new 2018 iPhone Xr, iPhone Xs, and Xs Max for $100 off MSRP. Their discount reduces the cost of an Xs to $899 for the 64GB models and $999 for the 64GB Xs Max. Price... Read more

Jobs Board

*Apple* IOS Systems Engineer - Randstad (Uni...
Apple IOS Systems Engineer **job details:** + location:Irvine, CA + salary:$45 - $55 per hour + date posted:Tuesday, July 16, 2019 + job type:Temp to Perm + Read more
Business Development Manager, *Apple* Globa...
Business Development Manager, Apple Global Tampa, FL, US Requisition Number:73805 As a Global Apple Business Development Manager at Insight, you proactively Read more
*Apple* Systems Architect/Engineer, Vice Pre...
…its vision to be the world's most trusted financial group. **Summary:** Apple Systems Architect/Engineer with strong knowledge of products and services related to Read more
*Apple* Graders/Inspectors (Seasonal/Hourly/...
…requirements. #COVAentryleveljobs ## Minimum Qualifications Some knowledge of agricultural and/or the apple industry is helpful as well as the ability to comprehend, Read more
Best Buy *Apple* Computing Master - Best Bu...
**710003BR** **Job Title:** Best Buy Apple Computing Master **Job Category:** Store Associates **Location Number:** 000171-Winchester Road-Store **Job Description:** Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.