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Conference ilbbak::ibi_focus

Title:	FOCUS, from INFORMATION BUILDERS

Moderator:	ZAYIUS::BROUILLETTE

Created:	Thu Feb 19 1987
Last Modified:	Mon May 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	615
Total number of notes:	1779

52.0. "How big is BIG ??" by MEMV04::SHELTRY (Wayne - MEM Finance IS - Acton) Thu Mar 31 1988 09:37

    Hello FOCUS users,
    
    	I'm in the process of collecting information on what a large
    FOCUS system is made up of, hence "How big is big?".  I'm working
    on an application now that I consider to be the largest I've seen
    within Digital.  It's made up of 20+ databases and over 400 .FEX
    procedures.  Is that big to the rest of the Digital FOCUS community?
    Do you have applications that are close to that size or bigger?
    
    	This is more or less a survey of what other FOCUS systems look
    like within Digital.  Will appreciate whatever information you can
    give me.
    
    Wayne

T.R	Title	User	Date	Lines
52.1	BIG POINTS TO DESIGN ISSUES	FDCV19::TRACE	`Fri Apr 01 1988 11:49`	18
	I DON'T THINK OF BIG AS THE NUMBER OF FOCUS FILES OR FEX'S BUT AS THE TOTAL AMOUNT OF DISK SPACE IN BLOCKS USED BY A SYSTEM, AND THE NUMBER OF SEGMENT INSTANCES IN FOCUS FILES. WHEN FOCUS FILES GET BIG (50,000 TO 100'S OF THOUSANDS OF BLOCKS) THEN DESIGN ISSUES BECOME THE CRITICAL FACTORS, WHETHER THERE'S 10 FEX'S OR 100 FEX'S 1 .FOC OR 20 . I'VE NEVER REALLY COUNTED THE FEX'S OR DISK BLOCKS IN THE APPLICATIONS I'VE WORKED ON BUT I'LL GUESSTIMATE A COUPLE: GENERAL LEDGER - 25-30 .FOC'S 250,000 BLOCKS 150 FEX'S TRACE - 15 .FOC'S 200,0000 BLKS 50 FEX'S MAYBE THIS SHOULD LEAD INTO A DISCUSSION OF DESIGN ISSUES . WILL ANYONE TAKE IT FROM HERE?? RICHARD MADDEN
52.2	What is large?	TIGEMS::GIRARD	`Mon Apr 04 1988 15:44`	31
	I agree with the fact that the number of FOCUS databases and Focexecs do not indicate how large a system, but the size of those databases and focexecs do. We currently have a few large FOCUS databases. We have 20 - 25 in total and five a relatively large. Two are 200,000 blocks, one is 325,000 and two are 400,000. I am also aware of a group in Westford with FOCUS databases spanning disk packs. Of course, with the use of these large files come the FOCUS problems never before encountered. A problem we ran into had to do with indexing. For your information, with release 1.3 or lower, if your index physically is located on a FOCUS page beyond 32,000 (use FDT to find out), then when using the indexing for a value on those pages will put you in a loop. Release, 1.31A fixed that problem and we discovered a new one. If referencing an index value from a page beyond 32,000 and it is the first value on the page, the message, 'invalid index pointer' will be generated from FOCUS. This problem is now fixed and will be in release 5.2. The way around these problems is with location files. Just make sure that the index page is not beyond 32,000. Has anyone run into any other problems or defficiencies with using large FOCUS databases? Has anyone converted any of these large files to RDB? Regards, Bob Girard.
52.3	More on design considerations	PLANIT::RYAN	`Thu Aug 04 1988 19:23`	14
	I agree with Richard and Bob - 'big' means database size - not appication programs. When FOCUS databases become large (i.e. >100k blocks) then design is everything. The VAX environment just makes you a lot more aware of design issues: breaking data into several physical files, more segments, unique segments, moving physical files onto more than one disk to avoid contention problems, changing the disk cluster size, watching your disk's fragmentation) - all radically effect performance. There are plenty of large applications running in FOCUS. The Area Info Center has databases per year which when concatenated with a USE statement, produce a logical 600k block database that is suprisingly efficient.. -rpr-