The following sections introduce some of the features that make the NetWare Btrieve record management system uniquely powerful.

Index Maintenance

NetWare Btrieve automatically creates and maintains the indexes in your files as you insert, update, and delete records. In addition to automatic index maintenance, NetWare Btrieve supports the following index features:

• Up to 119 key segments per file
• Adding or dropping any index after a file has been created
• Numerous data types for key values: integer, float, date, time, decimal, money, logical, numeric, bfloat, string, lstring, zstring, unsigned binary, autoincrement, and signed trailing separate
• Numerous key attributes: linked/repeating duplicatable, duplicatable/nonduplicatable, supplemental, modifiable/nonmodifiable, segmented/nonsegmented, descending/ascending sorting, case-sensitive/case-insensitive sorting, alternate collating sequence, null (any-segment/all-segment)/non-null

File Specifications

NetWare Btrieve allows you to create Btrieve (data) files by using either function calls (from an application) or the Btrieve Maintenance utility (BUTIL) commands. NetWare Btrieve offers these file specifications:

• File sizes up to 4 billion bytes (4 gigabytes)
• Number of records limited only by the size limit of the file
• Consistent file definition and management routines independent of the operating environment
• Consistent file structures

The cache is an area of memory that NetWare Btrieve reserves for buffering the pages that it reads. The cache is divided into a number of buffers, each of which is initially the size of the largest page the application will access. NetWare Btrieve calculates this size using the maximum page size and the memory options you define when you configure NetWare Btrieve.

Generally, a larger cache improves performance because it allows more pages to be in memory at a given time. NetWare Btrieve allows you to specify the amount of memory to reserve for the I/O cache buffers.

To determine this amount of memory, take into consideration the following factors:

• The application's memory requirements (if the application is an NLM)
• The total amount of memory installed on the workstation (for client-based Btrieve) or on your server (for NetWare Btrieve)
• The combined size of all files the application will access

When your application requests a record, NetWare Btrieve first checks the cache to see if the page containing that record is already in memory. If so, NetWare Btrieve transfers the record from the cache to the application's data buffer.

If the page is not in the cache, NetWare Btrieve reads the page from the disk into a cache buffer before transferring the requested record to the application.

If every cache buffer is full when NetWare Btrieve needs to transfer a new page into memory, a least-recently-used (LRU) algorithm determines which page in the cache Btrieve should overwrite. The LRU algorithm reduces processing time by keeping the most recently referenced pages in memory.

When an application inserts or updates a record, NetWare Btrieve first modifies the corresponding page in the cache and then writes that page to disk. The modified page remains in the cache until the LRU algorithm determines that Btrieve can overwrite the image of that page in cache with a new page.

Data Integrity

The following NetWare Btrieve features let you support concurrent access while ensuring the integrity of your files in a multiuser environment:

NetWare Btrieve provides the following capabilities for enhancing data security in a network environment:

• Assigning owner names to files
• Specifying dynamic encryption and decryption of data
• Providing NetWare file-level security through the NetWare Btrieve Requesters