Glossary of Terms
The audit file number is a four-digit number that identifies an audit file.
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.
Note: 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.
DATABridge Accessories access the services in DBEngine and DBSupport. Some of the Accessories provided with DATABridge are as follows:
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.
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.
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.
The Batch Console automates routine Client tasks by allowing command files/shell scripts launched by the Client service to interact with the service.
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.
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 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.
A file created by DATABridge Span that contains all replicated records from various data sets.
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:
Data and Structure Definition Language (DASDL) is the language that defines DMSII databases. The DASDL must be compiled to create a DESCRIPTION file.
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 (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.
The DATABridge Engine (also referred to as DBEngine) is a host library program that provides several entry points for retrieving both data definition and data records from a DMSII database. To provide this information, DBEngine reads the DMSII DESCRIPTION file, the CONTROL file, and the audit trail. DBEngine uses the services of the Accessroutines to retrieve data from the database for the initial cloning.
DATABridge Plus is an optional program that enables DATABridge to access and retrieve information from the current audit file. If you have not set Read Active Audit = true, the most recent audit file DATABridge can read is the current audit file minus one. For example, if the current audit file number is 23, DATABridge can access audit file number 22 (23 - 1).
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:
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.
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.
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.
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.
A procedure in a library object.
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.
A DMSII filler substitution is a technique for avoiding a reorganization. It changes record layouts, but does not move records around.
Changes that occur to the DMSII database while a clone is taking place.
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 Name and 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.
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.
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.
A DATABridge Host accessory that produces a report of the layout of the structures in your DMSII database, including structure numbers and key sets.
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.
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.
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.
Structural or formatting changes to records in the DMSII database, which may require parallel changes to (or re-cloning of) records in the secondary, or relational, database. See also file format conversion and record format conversion.
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 is the ongoing process of cloning and tracking changes to a DMSII database.
A systematic restoration of the primary or secondary database to a previous state in which the problem or bad data is no longer found.
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.
Operating system resources that are mainly used to implement thread synchronization and signaling.
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.
An index into a data set. A set has an entry (key + pointer) for every record in the data set.
Data that reflects information about the cloned data, such as the audit location and format level.
A data set, set, subset, access, or remap. Each structure has a unique number called the structure number.
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.
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.
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.
A data structure in the client database corresponding to a data set or remap in the host DMSII database.
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.
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.