Product Documentation

Database Administrator's Guide

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This Appendix provides definitions for some of the terms found in this guide. Most terms are discussed in further detail throughout the rest of the guide. The definitions considered for the advanced user are depicted by listing “(advanced)” at the beginning of the definition.

Individual typically responsible for installing, configuring, starting, stopping and maintaining the database Server and the files controlled by the FairCom DB Server.

ASCII Text File
“ASCII” is an industry code for representing characters as binary values. An ASCII Text File is a special type of file that can be copied from computer to computer and read by most word processors and editors. If this file type is unfamiliar, consult the word processor or editor documentation for additional information.

atomicity (advanced)
A term meaning an all or nothing criteria applied to data inserts, deletes and updates; with the principal goal of keeping a group of files synchronized. For example, if a record is to be updated in a series of five files as follows:

enable transaction

file 1 update - successful

file 2 update - successful

file 3 update - error, not updated

file 4 update - successful

file 5 update - successful

commit transaction

In this example, the failed update for file 3 will cause the commit transaction to fail. Atomicity indicates this failure on file 3 will prevent any updates from occurring. Without atomicity, files 1, 2, 4 and 5 would have been updated, but file 3 would not, causing the five files to be out of sync.

automatic recovery
The process of restoring files back to a pristine state after some type of catastrophe (i.e., loss of power to the computer). Automatic recovery is available only for files using full transaction processing (TRNLOG file mode). The TRNLOG file mode causes all of the changes to the particular file to be logged immediately to a special high-speed transaction log. The presence of this complete history of the changes to the data files with the TRNLOG file mode is what makes automatic recovery possible.

The amount of computer memory required to store one character. To store the word “computer” takes 8 bytes. Computer memory and hard disk space are often measured in kilobytes or megabytes. 1 kilobyte = 1024 bytes (characters) = 210; 1 megabyte = 1048576 bytes (characters) = 220.

A storage location where data can be more quickly accessed. For example, a disk cache will store frequently accessed data in memory to prevent reading from the slower disk drive.

FairCom DB
The c-tree file handler API that is the foundation of the c-tree database Server. FairCom DB also serves as the client side development kit for the c-tree client/server model. FairCom DB gives a client side application the ability to communicate (connect) with the FairCom DB Server.

(advanced) An entry placed in FairCom DB Server logs identifying a starting point during the Server’s automatic disaster recovery.

The second half of the client/server model. The client process is typically a third party application performing a specific task. For example, in a client/server based accounting system, the program prompting the user for input and displaying results would be considered a client.

FairCom DB Server utility program allowing the Server Administrator to grant access to the Server through user identification names. Controls high-level access to the Server and should be executed by the Server Administrator only.

FairCom DB Server utility program for creating file backups. This unique utility allows the backup of user data to be performed without restricting user access in any way.

FairCom DB Server utility program for rolling forward from a specific point in the transaction log history. The FairCom DB Server has the ability to allow users to reset files to specific points in time. This utility allows older backups of user data to be brought up to date.

ctldmp (advanced)
FairCom DB Server utility program for displaying detailed information from the Server transaction logs.

FairCom DB Server utility that restores the backups made using ctdump. This utility also performs data rollbacks.

FairCom DB Server utility to allow users to change their password.

FairCom DB Server utility for stopping the FairCom DB Server.

data file
A collection of similar pieces of information stored in one location.

deadlock (advanced)
A situation in which two users are prevented from obtaining access to the same record. An example of this situation is if user A locks record 1 for update. At the same time, user B locks record 2 for update. User A now needs to lock record 2 and user B needs to lock record 1. If user A and B both need locks on their target records before processing can continue, a deadlock occurs. The FairCom DB Server automatically handles this situation by returning error messages to the users involved.

A location where files are stored on disk. A directory can be thought of as a hanging folder in a file cabinet. Each file folder within the hanging folder can be thought of as a separate file, or collection of information.

dynamic dump
A method for backing up specified files without restricting user access to the files.

Disguising information making it difficult for a casual user to inspect the actual contents.

The COMM_PROTOCOL keyword for specifying the TCP/IP transport protocol.

The COMM_PROTOCOL keyword for specifying the TCP/IP transport protocol using an IPv6 socket.

(Deprecated) The COMM_PROTOCOL keyword for specifying the TCP/IP transport protocol with CAMO. CAMO or "Camouflage" is an older, legacy method of hiding data, which is not a standards-conforming encryption scheme, such as AES. It is not intended as a replacement for Advanced Encryption or other security systems.

The COMM_PROTOCOL keyword for specifying the shared memory transport protocol.

A collection of related information, referred to as records. See the definitions for directory and record for further information.

The Apple Macintosh term for a location of files on disk. Similar to directory defined above.

hash bins (advanced)
A mathematical algorithm for storing data in memory so it can be quickly located and retrieved. The FairCom DB Servers all use sophisticated hashing routines for data and index caches.

index file
A special type of file used by FairCom DB and the FairCom DB Server for quickly locating information (records) within a data file.

log (ctstatus, transaction)
A special purpose file containing important information about a specific process. For example, the c-tree CTSTATUS log will contain status information about the Server. Storing items such as when the Server was last started and stopped and what files have been backed up using the dynamic dump facility, etc.

The process of keeping a permanent record of the changes made during a transaction.

message queues
A communication protocol typically used on Unix based operating systems. This communication protocol allows a client process to talk to a FairCom DB Server process.

A mechanism for duplicating important files on different hard drive volumes, partitions or physical devices. If the primary storage location is lost due to some form of catastrophe (i.e., hard disk crash) the mirroring logic can automatically detect the lost connection and switch to the secondary or “mirrored” storage area without any user intervention.

NetBIOS (Network Basic Input/Output System)
A communication protocol that was typically used on legacy Microsoft based operating systems. This communication protocol has been deprecated.

page (advanced)
A unit of measure for electronic data. At the lowest level operating system read and write, data is manipulated in page sizes. A common page size for Windows and Unix is 4096 bytes.

PREIMG (advanced)
A transaction processing file mode supporting atomicity, but not automatic recovery.

For purposes of this Guide, a process is equivalent to a user or connection. One process equals one user.

A piece of information stored within a file. Expanding on the file cabinet example used in the directory definition, each piece of paper found within a file folder can be thought of as a record. A record is a unique piece of information similar to other pieces of information (papers) within the same file folder.

roll back
A process made possible with transaction processing allowing file transactions to be reset back to a specific point in time. For example, if a data entry operator enters two hours' worth of transactions with incorrect information, these transactions can be removed or rolled back.

roll forward
Similar to roll back, except moving forward in time. The roll forward process is typically for applying transactions to “out dated” (old) files. To do this transaction processing logs containing the desired transactions must be available.

semaphore (advanced)
An operating system level counter used for controlling access to a limited pool of shared resources, such as shared memory.

The term server can refer to many different items. For example, a “file server” is a specific piece of software for sharing files and hardware devices among users. A “hardware server” is a special computer on which the file server operates. The FairCom DB Server is a “database server”, special software efficiently managing multiple users accessing common data.

shared memory
A communication protocol typically used on Unix and Windows based operating systems. This communication protocol allows a client process to talk to a FairCom DB Server process.

A physical file containing any number of logical data and index files.

The tar command is used for creating and managing file backups. FairCom DB Unix Servers are shipped in tar format. The tar command is used to copy the files from the distribution floppies to the hard drive.

Transport Control Protocol/Interface Program. A communication protocol available on most operating systems. This communication protocol allows a client process to talk to a Server process.

A specific operation on a file (i.e., adding a record, deleting a record, updating a record - are all examples of a transaction).

transaction processing
A mechanism by which several data integrity issues are handled. Two of the most important issues are atomicity and automatic recovery.

A client process (application) connected to a FairCom DB Server. Each process connected to a FairCom DB Server is counted as a user.

working directory
The directory pointed to by the LOCAL_DIRECTORY keyword in ctsrvr.cfg, or (if not specified) the directory where the FairCom Server process resides.