Enscribe Programmer's Guide

This manual describes the use of the Enscribe software with the DP2 disk process. Some of the
most notable Enscribe features are:
• Five disk file structure types:
unstructured◦
◦ key-sequenced:
legacy key-sequenced (1 to 16 partitions, file format 1 and 2)–
– legacy key-sequenced with increased limits (1 to 16 partitions, larger record size,
larger block size, larger key size, file format 2 only)
– enhanced key-sequenced (17 to 64 partitions, file format 2 only)
– enhanced key-sequenced with increased limits (17 to 128 partitions, larger record
size, larger block size, larger key size, file format 2 only)
◦ queue
◦ entry-sequenced
◦ relative
• File Formats: format 1 and format 2
• Partitioned (multiple-volume) files
• Multiple-key access to records
• Relational access among files (where a field value from one file is used as a key to access a
data record in another file)
• Optional automatic maintenance of all keys and optional key compression in key-sequenced
data or index blocks
• Support of transaction auditing through the NonStop Transaction Management Facility (TMF).
• Optional compression of audit-checkpoint records
• Record locking and file locking
• Cache buffering
• Optional sequential block buffering
Terminology
To create and use Enscribe files, you should be familiar with these terminologies:
• File: a collection of related records, physically organized as a number of extents on disk, that
is referenced by a Guardian file name. Structured files (entry-sequenced, key-sequenced,
queue, and relative files) are further subdivided into blocks of records.
• Format 1 and 2: Format is a static attribute of a file and is established when the files is created.
Format 2 files, introduced with the D46 release, differ from format 1 files in these ways: larger
partitions than the current 2 GB minus 1 MB format 1 file partition and larger primary keys
and alternate-key records for relative and entry-sequenced files.
• Logical record: the unit of information transfer between your application program and the file
system; unless you are using sequential block buffering, the logical record is also the unit of
information transfer between the file system and the disk process. The maximum logical record
size is specified as a number of bytes.
• Sector: the smallest unit of disk I/O or physical addressing (512 bytes in length for all currently
supported disk drives).
Terminology 19