PowerPatch 5 brought bounty, but the new MDX has a gotcha

September 1998

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PowerPatch 5 brought bounty, but the new MDX has a gotcha
Customers took delivery and installed PowerPatch 5 for MPE/iX 5.5, with its consolidation of new 3000 features and improvements like dynamic master dataset expansion (MDX). It didn’t take long after the software’s Communicator was shipped for Adager to report that MDX will do some hashing you might not have the time or resource to handle while MDX automatically expands master dataset capacities. Alfredo Rego mentioned the problem in his HP World talk on IMAGE/SQL, and partner Rene Woc outlined the details which database administrators will want to watch for.

MDX makes sure that the hashing capacity is a multiple of the dataset’s blocking factor, just like the dynamic detail dataset expansion (DDX) feature. “That’s fine if you’re starting a brand new database,” Woc said. “But if you have an existing database and you want to enable MDX, then most likely your hashing capacity will not be a multiple of the blocking factor.” Other than the rare instance where your dataset’s hashing capacity is one, “in order to make it a multiple of the blocking factor, since the location of all the entries are functions of that hashing capacity, they will have to be re-hashed,” Woc said. “It’s not a hashing problem, it’s the need for rehashing and the time involved.” Woc said that a master dataset with 5,000 entries would only take a fraction of a second. Trouble is, most people who’d use MDX have datasets many times bigger than that, meaning many, many times longer than a fraction of a second for each dataset expanded.

“We figure the people most likely candidates for MDX are big shops that can’t afford the time to re-hash,” Woc said. Datasets with millions of entries are getting more common all the time, especially in the healthcare and direct mail markets where the 3000 is gaining new customers. HP has agreed to modify IMAGE/SQL code in a patch or future release, so MDX will not be required to have a hashing capacity which is a multiple of the blocking factor. No, it won’t be the first release of MPE/iX 6.0; that code is well locked down by now, poised for shipment in late October.

Woc said HP told him the fix will be available as a patch soon after 6.0 ships. Adager’s Rego said that after studying the problem for four months, he had devised an algorithm to offer the big shop, MDX-using community a fix well before that post-6.0 patch. “I came up with an Adager solution that allows you to enable a master dataset for MDX — under the current IMAGE release — even when its capacity is not a multiple of its blocking factor, provided a little easy-to-meet condition is met,” he said. “There will be rare cases where this easy-to-meet condition cannot be met.” The Adager solution applies only to existing master datasets you enable for MDX on the fly. If you create a new MDX dataset from scratch via DBSCHEMA and DBUTIL, IMAGE will still round up its capacity (if necessary) to be a multiple of the dataset’s blocking factor. Rego reported via the Internet that he was polishing his algorithm before releasing the fix.

Copyright 1998 The 3000 NewsWire. All rights reserved




		Click here for SolutionSoft sponsor message
		PowerPatch 5 brought bounty, but the new MDX has a gotcha Customers took delivery and installed PowerPatch 5 for MPE/iX 5.5, with its consolidation of new 3000 features and improvements like dynamic master dataset expansion (MDX). It didn’t take long after the software’s Communicator was shipped for Adager to report that MDX will do some hashing you might not have the time or resource to handle while MDX automatically expands master dataset capacities. Alfredo Rego mentioned the problem in his HP World talk on IMAGE/SQL, and partner Rene Woc outlined the details which database administrators will want to watch for. MDX makes sure that the hashing capacity is a multiple of the dataset’s blocking factor, just like the dynamic detail dataset expansion (DDX) feature. “That’s fine if you’re starting a brand new database,” Woc said. “But if you have an existing database and you want to enable MDX, then most likely your hashing capacity will not be a multiple of the blocking factor.” Other than the rare instance where your dataset’s hashing capacity is one, “in order to make it a multiple of the blocking factor, since the location of all the entries are functions of that hashing capacity, they will have to be re-hashed,” Woc said. “It’s not a hashing problem, it’s the need for rehashing and the time involved.” Woc said that a master dataset with 5,000 entries would only take a fraction of a second. Trouble is, most people who’d use MDX have datasets many times bigger than that, meaning many, many times longer than a fraction of a second for each dataset expanded. “We figure the people most likely candidates for MDX are big shops that can’t afford the time to re-hash,” Woc said. Datasets with millions of entries are getting more common all the time, especially in the healthcare and direct mail markets where the 3000 is gaining new customers. HP has agreed to modify IMAGE/SQL code in a patch or future release, so MDX will not be required to have a hashing capacity which is a multiple of the blocking factor. No, it won’t be the first release of MPE/iX 6.0; that code is well locked down by now, poised for shipment in late October. Woc said HP told him the fix will be available as a patch soon after 6.0 ships. Adager’s Rego said that after studying the problem for four months, he had devised an algorithm to offer the big shop, MDX-using community a fix well before that post-6.0 patch. “I came up with an Adager solution that allows you to enable a master dataset for MDX — under the current IMAGE release — even when its capacity is not a multiple of its blocking factor, provided a little easy-to-meet condition is met,” he said. “There will be rare cases where this easy-to-meet condition cannot be met.” The Adager solution applies only to existing master datasets you enable for MDX on the fly. If you create a new MDX dataset from scratch via DBSCHEMA and DBUTIL, IMAGE will still round up its capacity (if necessary) to be a multiple of the dataset’s blocking factor. Rego reported via the Internet that he was polishing his algorithm before releasing the fix. Copyright 1998 The 3000 NewsWire. All rights reserved