### VOSS 3.0

VOSS adds transparent database management to IBM VisualAge® Smalltalk. Multi-user applications can access distributed persistent objects by normal message sending in atomic transactions, with none of the complexity and performance cost of mapping objects to relational tables. Transaction integrity is assured by two-phase commit with logging for rollforward crash recovery. VOSS provides the means to use persistent objects as though normal language objects, and with the transaction processing of a database management system.

Fully automatic object locking, caching and change-detection maximise concurrency and performance whilst minimising the intrusion of database management functions into the application. This makes it easy to convert single-user prototypes to multi-user applications.

Benefits

- Secure transaction processing with virtual Smalltalk objects.
- Design your objects to suit the application, not the storage system.
- No database language to learn, just ordinary Smalltalk in open-ended or [...] atomic block transactions.
- Easy conversion of prototypes to finished applications.
- Normal use of the Smalltalk debugger in development.

Features

- Transactions may include objects in multiple virtual spaces on different servers, with mixed R/W & R/O (CDROM) files, and R/W or R/O log-on per client.
- Two-phase commit and transaction logging for rollforward crash recovery.
- Designer control of virtual object granularity/clustering.
- Automatic change detection.
- Automatic object locking, with user-specified degree of transaction isolation for either
  - Complete Isolation, or
  - High Concurrency, with either
    - Repeatable Read, or
    - Minimum Memory Use (e.g. for long report-generating transactions)
- Continuous automatic lock retry until time-out relieves the application from having to handle temporary lock conflicts.
- Absence of lock conflicts between nested transactions and their parents allows easy re-use of existing source code.
- Timestamp-refreshed retrieval and pre-allocation caches in the client minimise network traffic and disk head movement.

- Virtual B-tree collections provide high performance access to very large numbers of objects. These include the multi-key/multi-value VirtualDictionarySet with set union & intersection query-building methods.

- Distributed concurrent background garbage-collection minimises down-time; a R/O virtual space needs no garbage-collection.

- Virtual object special features include historical versioning, alternative futures, replication, check-out, identity exchange, commit timestamp, read-only flag (attempted change forces rollback on commit), user-defined proxies, low-level peek/poke etc.

- Schema modification.

- Control Panel for database administration: current user information, backup, restore, logging, rollforward, cache size & garbage-collection tuning etc.

- Compatible with Smalltalk Systems WindowBuilder Pro®.

Source code is included for most public methods, the collections, object replication and the control panel; other documentation includes interactive tutorial and discussion of object database design in Smalltalk. Development licences include 60 days free technical support. Single-payment unlimited runtime distribution depending on the required number of concurrent users per virtual space.

Please see our web site for more information.

| Logic Arts Ltd Cambridge CB1 3BY England UK Tel: +44 1223 212392 Fax: +44 1223 245171
E-mail: info@logicarts.com
Web: http://www.logicarts.com

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