Drew Wutka
DWUTKA at marlow.com
Fri Feb 2 11:32:20 CST 2007
The Jet LDB white paper explains it. Essentially the .ldb is going to be 64 bytes per user. Each chunk is 32 bytes for the machine name, 32 bytes for the Access User name. Then there is a chunk of bytes in the .mdb itself, 2 or 4(not sure about Jet 4.0, I haven't seen a white paper on it) byte chunks, and there are 255 of them. (The max number of users). The first chunk (in the .mdb) relates to the first 64 byte chunk in the .ldb. The smaller chunks in the .mdb are changed based on the users activity. Actual record locks on the database are stored in the .ldb too, but in a very odd way. When I first read about it, I thought it was the oddest thing. Basically, the max size of an .ldb is going to be 16k. (255*64). However, there is a 'virtual' size of the .ldb. If Jet needs to lock something in the 25th megabyte of an .mdb, it creates a lock on that position in the 'virtual .ldb', even though the .ldb isn't that big, file read/write code can lock bits outside a file's actual space. This prevents any read/write locks on the actual .mdb. Drew -----Original Message----- From: JWColby [mailto:jwcolby at colbyconsulting.com] Sent: Friday, February 02, 2007 10:31 AM To: 'Access Developers discussion and problem solving' Subject: Re: [AccessD] Connections and Performance No, but the lock file does (LDB). I have never really figured out how. If you open it in a text editor it is mostly empty. John W. Colby Colby Consulting www.ColbyConsulting.com -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Charlotte Foust Sent: Friday, February 02, 2007 11:20 AM To: Access Developers discussion and problem solving Subject: Re: [AccessD] Connections and Performance I've certainly had more than 5 FEs connected to a single BE. The back end doesn't keep track of connections in Access. Charlotte Foust -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Dan Waters Sent: Friday, February 02, 2007 5:58 AM To: 'Access Developers discussion and problem solving' Subject: [AccessD] Connections and Performance I've read several times that maintaining a connection between a FE and a BE will increase the performance of the FE because it doesn't need to reconnect before transferring data. The connection here would be a bound form connected by a table link to a table in the BE. But, the connection limit for one BE is 5 FE's. So, will maintaining connections on more than 5 FE's reduce performance? Seems logical, but I was wondering if this is correct or is there more to it? Thanks! Dan Waters -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com