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Conference ulysse::rdb_vms_competition

Title:	DEC Rdb against the World

Moderator:	HERON::GODFRIND

Created:	Fri Jun 12 1987
Last Modified:	Thu Feb 23 1995
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1348
Total number of notes:	5438

889.0. "Does Ingres do Asyncronous I/O ?" by BATMAN::LEBLANC (So many notem, so little time) Thu Mar 14 1991 10:24

	Rdb does its I/O syncronously.  It can only perform Asyncronous I/O
	during a COMMIT operation.  

	I am trying to win against Ingres in a TP situation (Ingres have ref. 
	sites using ACMS).

	What I want to know is:  Do the Ingres server processes do their IO
	syncronously or asyncronously on the database....because if its
	syncronous then we have a MAJOR advantage in using ACMS with Rdb over 
	INGRES as the ACMS servers still have to go through the INGRES detached
	processes to get to the database.

	Thanks for any info,
	.Bill

T.R	Title	User	Personal Name	Date	Lines
889.1	Ingres server I/O is asynchronous	BEAGLE::GODFRIND	TSCG, Valbonne VBO1-2/B15 DTN 828-5163	`Fri Mar 15 1991 18:29`	12
	I take it you mean Ingres on VMS ? I know that Ingres on Ultrix has to resort to a trick to get asynchronous writes (because the O/S does not provide them) - it uses a set of child processes (slaves) to do the I/O, thus freeing the DBMS servers to do something else while the I/O proceeds. If I am not mistaken, the servers on VMS also do asynchronous I/O. If you think about it, how could they _not_ do so ? What would be the point of having multithreaded servers if all I/O was single-threaded ? /albert
889.2	Theory vs practice...	BROKE::HIGGS	SQL is a camel in disguise	`Fri Mar 15 1991 20:36`	9
	Isn't the point that Rdb/VMS with ACMS should be able to outperform INGRES with ACMS, in practical situations? Whether a database uses synchronous or asynchronous writes is simply a technique. What counts is results, surely? Or does the customer need theoretical arguments to be convinced? Bryan
889.3	Ingres logfile writes must be synchronous	BIGUN::PHILLIPS	Blair Phillips, SI, Canberra, Oz	`Sun Mar 17 1991 10:12`	9
	Even if Ingres does async i/o elsewhere, it still needs to do synchronous writes to its logfile when committing a transaction. Ingres uses a single logfile for all databases on the system, so this file is a real hot spot in a high update environment. (And no, you can't put it on a RAM disk, it is essential to database integrity. ESE20 would be a good move, though.) Blair
889.4	but what about ...	WARNUT::BRYAN		`Mon Mar 18 1991 12:00`	6
	As an aside, what about the lack of row level locking and the fixed page size, don't these detract from using Ingres in a TP environment. Not to mention performance ownership problems. What do they gain by using the Ingres db ?