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Glossary of Terms

ABSN

Audit block serial number---The audit block serial number is a 10-digit number that identifies an audit block.

absolute address (AA) value

AA is a DMSII term that stands for absolute address. An absolute address value is an A Series WORD (48-bits in length). In the Databridge Client, AA is the hexadecimal representation (12 character strings containing the characters 0--9 and A--F) of the AA value on the host. Databridge Client uses the AA values to implement unique keys for the parent structures of embedded data set records. It also uses AA values to reference the records of data sets that do not have DMSII SETS with the NO DUPLICATES ALLOWED attribute.

AA values are not constant. Any DMSII reorganization (record conversion, file format, or garbage collection) changes these values.

Databridge Client supports numeric AA values that are stored as NUMBER(15) in Oracle, BIGINT in SQL Server, and DECIMAL(15) in DB2. It also supports binary AA values that are stored as RAW(6) in Oracle and BINARY(6) in SQL Server.

accessories

Databridge accessories access the services in DBEngine and DBSupport. Some of the accessories provided with Databridge are as follows:

  • DBServer, which provides communication and DMSII database replication services to Databridge Clients.

  • DBSpan, which produces a replication of one or more data sets into flat sequential disk files. DBSpan updates the cloned flat files by appending the changes to the end of the flat files (unlike DBSnapshot, which replaces the changed records).

  • DBSnapshot, which produces a one-time replication of one or more data sets into flat sequential disk files or tape.

  • DBTanker, which provides filtered audit files for the DBSpan and DBServer accessories.

  • DBInfo, which produces a report of your DMSII database timestamps, update levels, DMSII release levels, etc.

  • DBLister, which produces a report of the layout of the structures in your DMSII database, including structure numbers and key sets.

  • DBAuditTimer, which closes the current audit file when it is older than a specified length of time.

Accessroutines

The Accessroutines program is a DMSII library program that controls access to the database, reads and writes records, and creates the audit trail.

Databridge Plus enables Databridge to perform near real-time replication of DMSII databases by accessing the audit file while the Accessroutines program is creating it.

AFN

The audit file number is a four-digit number that identifies an audit file.

audit file

An audit file is created by the DMSII Accessroutines and contains the raw format of changes made to the DMSII database by update programs. Audit file records contain the deletes, creates, and modifies that were made to the various structures. Depending on the frequency of changes made to a database, the information in an audit file can span a few hours or several weeks.

Databridge uses the audit file for the raw data of each database change to exactly replicate the primary database. Databridge records the audit location (AFN, ABSN, SEG, IDX) between runs, so it can restart without losing any records.

audit trail

The audit trail contains all of the audit files generated for a database. The Databridge Engine reads the audit files to extract updates. It then passes the updates to the Client to be applied to the relational database. After the updates have been successfully extracted, the Client saves the state information, which includes the location in the audit trail from which the last group of updates for the data set were read.

Batch Console

The Batch Console automates routine Client tasks by allowing command files/shell scripts launched by the Client service to interact with the service.

caching

A process that filters files before they\'re requested by the Databridge Client. Caching allows Databridge Enterprise Server to send Client data requests quickly and without placing an additional resource burden on the mainframe.

client

The client is the computer system that will receive DMSII records from the primary database. The client could be a Windows computer, a UNIX computer, or an MCP server. The client can have a relational or a DMSII database.

cloning

Cloning is the one-time process of generating a complete snapshot of a data set to another file. Cloning creates a static picture of a dynamic database. Databridge uses the DMSII data sets and the audit trail to ensure that the cloned data represents a synchronized snapshot of the data sets at a quiet point, even though other programs may be updating the database concurrently. Databridge clones only those data sets you specify.

Cloning is one phase of the database replication process. The other phase is tracking (or updating), which is the integration of database changes since the cloning.

consolidated file

A file created by Databridge Span that contains all replicated records from various data sets.

CONTROL file

The DMSII CONTROL file is the runtime analog of the DESCRIPTION file. The DESCRIPTION file is updated only when you compile a modified DASDL. The CONTROL file controls database interlock. It stores audit control information and verifies that all database data files are compatible by checking the database timestamp, version timestamp, and update level. The CONTROL file is updated each time anyone opens the database for updates. The CONTROL file contains timestamps for each data set (when the data set was defined, when the data set was updated). It contains parameters such as how much memory the Accessroutines can use and titles of software such as the DMSUPPORT library (DMSUPPORT/databasename).

Databridge uses the CONTROL file for the following information:

  • Timestamps

  • INDEPENDENTRANS option

  • AFN for the current audit file and ABSN for the current audit block

  • Data set pack names

  • Audit file pack name

  • Database user code

DASDL

Data and Structure Definition Language (DASDL) is the language that defines DMSII databases. The DASDL must be compiled to create a DESCRIPTION file.

data set

A data set is a file structure in DMSII in which records are stored. It is similar to a table in a relational database. You can select the data sets you want to store in your replicated database.

Databridge Director

Databridge Director (also referred to as DBDirector) is a Windows Service installed with Enterprise Server that starts Enterprise Server whenever a connection request is received.

When you start your computer, DBDirector starts and reads the ListenPort registry value to determine which TCP/IP port communicates with Databridge Clients.

Databridge Engine

The Databridge Engine (also referred to as DBEngine) is a host library program that uses the DMSII Support Library to retrieve data records from the DMSII database for cloning.

DBClient

A Client program that is launched by the service. DBClient handles the processing of DMSII data and updates the same as dbutility, except that it runs as a background run and uses the Client Console to display its output and interact with the operator.

DBClntCfgServer

A program that handles all requests from the Client Console specific to a data source. These requests include updating the client configuration file, providing access to the client control tables, and handling the Client Configurator. Like DBClient, this program is run by the service as a background run.

GenFormat

A host utility that creates translation, filter, and format routines. The GenFormat utility interprets the GenFormat parameter file to generate ALGOL source code patches, which are included in the tailored Support Library.

DESCRIPTION file

The DESCRIPTION file contains the structural characteristics of a database, physically and logically. This file is created from the DASDL source by the DASDL compiler and contains the layout (physical description), timestamp, audit file size, update level, logical database definition, and any static information about the database. It contains information about the database, not the data itself.

There is only one current DESCRIPTION file for each DMSII database. Databridge must have access to the DESCRIPTION file before it can replicate a database. Additionally, Databridge uses the DESCRIPTION file information for consistency checks between the primary database and the secondary or replicated database.

The DESCRIPTION file corresponds to the schema in a relational database.

direct disk

A replication method that allows Databridge Enterprise Server to clone and track DMSII data sets without using any significant mainframe resources. Direct disk replication requires a SAN (Storage Area Network) or Logical Disks configured to make MCP disks visible in Windows.

entry point

A procedure in a library object.

extraction

Extraction is the process of reading through a data set sequentially and writing those records to a file (either a secondary database or flat file).

file format conversion

A type of DMSII reorganization affects file size values (for example, AREASIZE, BLOCKSIZE, or TABLESIZE), but it does not change the layout of the records in a DMSII database.

filler substitution

A DMSII filler substitution is a technique for avoiding a reorganization. It changes record layouts, but does not move records around.

fixup records

Changes that occur to the DMSII database while a clone is taking place.

flat files

A flat file is a plain text or mixed text and binary file which usually contains one record per line. Within the record, individual fields may be separated by delimiters, such as commas, or have a fixed length and be separated by padding. An example of a flat file is an address list that contains fields for Nameand Address.

garbage collection reorganization

A garbage collection reorganization moves records around, but it doesn't change the layout of the DMSII database. Its primary function is to improve disk and/or I/O efficiency by eliminating the space occupied by deleted records. Optionally, a garbage collection reorganization reorders the remaining records in the same sequence as one of the sets.

lag time

The lag time is defined as the elapsed time between the time a record in the DMSII database is updated and the time where this update appears in the relational database. This value accounts for any difference between the clock on the mainframe and that on the client machine.

Lister Accessory

A Databridge Host accessory that produces a report of the layout of the structures in your DMSII database, including structure numbers and key sets.

mutex

A mutex is an operating system resource that is used to implement a critical section and prevent multiple processes from updating the same variables at the same time.

null value

The value defined in the DASDL to be NULL for a data item. If the DASDL does not explicitly specify a NULL value for a data item, the NULL value is all bits turned on.

primary database

This is the original DMSII database that resides on the host. Databridge replicates from the primary database to one or more client databases. The client databases can be another DMSII database or one of several relational databases. Compare this to the replicated (or secondary) database.

quiet point (QPT)

A quiet point is a point in the audit trail when the DMSII database is quiet and no program is in transaction state. This can occur naturally, or it can be forced by a DMSII sync point.

record format conversion

A type of DMSII reorganization that occurs when a data set or set (group of keys) is reordered or reformatted. It indicates that changes were made to a data set format, or to data items, such as changing the length of an item, for example, BANK-ID NUMBER (10) to BANK-ID NUMBER (15).

record serial number (RSN)

Record sequence numbers (RSN) are 48-bit quantities used by the Databridge Engine, in the case of DMSII XE, to uniquely identify a record. RSNs will always be used instead of AA values when available except for data sets having embedded data sets. RSNs are always static; they will not change after a garbage collection reorganization.

replicated database

The replicated database is the database that usually resides on the client machine and contains records cloned from the DMSII database. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.

replication

Replication is the ongoing process of cloning and tracking changes to a DMSII database.

rollback

A systematic restoration of the primary or secondary database to a previous state in which the problem or bad data is no longer found.

secondary database

The replicated database. The replicated database is the database that usually resides on the client machine and contains records cloned from the DMSII database. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.

semaphores

Operating system resources that are mainly used to implement thread synchronization and signaling.

Databridge Server

Databridge Server (also referred to as DBServer) is a Databridge Host accessory that responds to Databridge Client requests for DMSII data or DMSII layout information and provides communications between the following components:

  • DBEngine and Databridge Enterprise Server

  • DBEngine and the Databridge Client

    Note

    When Enterprise Server is used with the Databridge Client, Enterprise Server takes over much of the functionality of DBServer and DBEngine.

service

The service (Windows) or daemon (UNIX) that automates most Client operations. It handles operator requests from the Client Console and routes all log and informational messages to the consoles.

set

An index into a data set. A set has an entry (key + pointer) for every record in the data set.

state information

Data that reflects information about the cloned data, such as the audit location and format level.

structure

A data set, set, subset, access, or remap. Each structure has a unique number called the structure number.

subset

An index into a data set. A subset does not necessarily have an entry (key + pointer) for every record in the data set. Subsets are used to access selected members of a data set and to represent relationships between data set records. Subsets typically contain fewer entries than normal sets.

An automatic subset is any subset that contains a WHERE clause and is maintained by DMSII.

A manual subset is any subset that is maintained by an application.

Support Library

A library that provides translation, formatting, and filtering to the DBServer and other accessories. After DBServer receives data from the Databridge Engine, it calls the Support Library to determine if the data should be replicated, and if so, passes the data to the Support Library for formatting.

system library

A library code file registered with the MCP on the host that is associated with a function name. Programs can link to the library code file by specifying the function name.

table

A data structure in the client database corresponding to a data set or remap in the host DMSII database.

tracking

Tracking is an ongoing process for propagating changes made to records in the DMSII primary database to the replicated database after the initial clone. The Databridge Engine performs extraction as well as tracking.

undigits

A NUMBER data item containing bit values from 10 to 15 in one or more digits. The digits in a NUMBER data item should contain values from 0 to 9; however, it is possible for the digits in NUMBER data item to contain values 0 to 15. Because values 10 to 15 are not valid digit values, the digits in NUMBER data items containing values from 10 to 15 are called undigits.