Glossary
Database Strategy glossary: hundreds of terms on Oracle, PostgreSQL, MySQL, data warehouse and project management with definitions and related articles.
A
Additive Measure
A numeric measure in a fact table that can be summed across all dimensions — amounts, quantities, counts. Fundamental in data warehouse design.
Agile Manifesto
A few-line document signed at Snowbird, Utah, on February 11-13, 2001 by seventeen developers. Four pairs of values that changed software development.
AI Manager
Professional role that governs the impact of artificial intelligence on architectures, processes and people within a project, separating real value from noise.
ALTER DOMAIN
Oracle 23ai command that modifies a SQL Domain (CHECK constraint, DEFAULT, annotations) propagating the change to all columns using the domain.
ALTER TYPE ADD VALUE
PostgreSQL command that appends a value to an existing ENUM. Metadata-only operation, transactional, no rebuild of the tables that use the type.
ANALYZE
The PostgreSQL command that updates table statistics used by the optimizer to choose the execution plan.
Annotations
Oracle 23ai metadata system that attaches key/value pairs to schema objects (columns, domains, tables), readable via USER_ANNOTATIONS_USAGE.
Anonymous User
MySQL/MariaDB user with no name created in some legacy installations. Represents a security risk as it can interfere with legitimate user matching.
ASH
Active Session History — Oracle component that records the state of every active session once per second, used for pinpoint performance diagnosis.
ASSERTION
SQL standard construct to express cross-table constraints validated at transactional level by the database engine. Announced in Oracle 26ai.
Authentication Plugin
MySQL/MariaDB module that handles the credential verification method during connection. The default changes between versions and can cause compatibility issues.
Autovacuum
PostgreSQL daemon that automatically runs VACUUM and ANALYZE on tables when the number of dead tuples exceeds a configurable threshold.
AWR
Automatic Workload Repository — Oracle Database's built-in diagnostic tool for collecting and analyzing performance statistics.
B
B-Tree
Balanced tree data structure, the default index type in most relational databases. Efficient for equality and range searches...
Binary log
MySQL's sequential binary record that tracks all data modifications, used for replication and point-in-time recovery.
Bloat
Dead space accumulated in a PostgreSQL table or index due to unremoved dead tuples, inflating disk size and degrading query performance.
Branch
Independent development line in a version control system. Allows working on isolated changes without affecting the main code until merge.
Brompton
British folding bicycle considered the world reference for build quality, folded compactness and practicality in urban commuting.
Bus Factor
Number of team members who, if simultaneously lost, would block the project. A measure of how concentrated critical knowledge is in a few heads.
Bus Matrix
Ralph Kimball's two-dimensional grid with business processes as rows and conformed dimensions as columns.
BYOL
Bring Your Own License — Oracle program that allows reusing existing on-premises licenses on OCI cloud without additional licensing costs.
C
Carbon Footprint
Total amount of greenhouse gases emitted directly or indirectly by an activity, expressed in tonnes of CO₂ equivalent
CDC
Change Data Capture — a technique for intercepting and propagating data changes in real time, often based on reading transaction logs.
CHECK constraint
Standard SQL constraint that restricts the values allowed in a column via a boolean expression. In MySQL it's only really enforced from version 8.0.16.
Churn
Measure of how much a database table changes after initial data insertion, in terms of UPDATEs and DELETEs. Determines the maintenance cost of indexes.
COALESCE
A SQL function that returns the first non-NULL value from a list of expressions.
Code Review
Practice of reviewing code by a colleague before merging, to catch bugs, improve quality and share knowledge within the team.
Commuting
Daily home-to-work travel and back, which in large Italian cities can absorb 2-4 hours per day and hundreds of euros per month in direct costs.
Compliance
Adherence to applicable regulations, rules and standards — in the AI context includes GDPR, industry regulations and internal policies on data and model usage.
Conformed Dimension
A dimension shared across multiple data marts with the same structure, semantics and key. Enables consistent, additive cross-process analysis.
CREATE TYPE AS ENUM
PostgreSQL DDL statement that creates an enumerated type as a first-class object, reusable across columns and modifiable via ALTER TYPE.
CTAS
Create Table As Select — Oracle technique for creating a new table populated with query results, used for migrations and restructuring of large tables.
Cutover
The critical moment in a migration when the production system is definitively moved from the old to the new infrastructure.
D
Daily Standup
Daily meeting of maximum 15 minutes where each team member answers three questions: what I did yesterday, what I will do today, what is blocking me.
Data Governance
Set of policies, processes and standards that ensure data quality, security and compliance within an organization.
Data Guard
Oracle technology for real-time database replication to a standby server, providing high availability and disaster recovery.
Data Mart
A subset of the data warehouse focused on a single business process or functional area. Often built independently by a department.
Data Warehouse
Centralised data collection and historicisation system from diverse sources, designed for analysis and business decision support.
Dead Tuple
Obsolete row in a PostgreSQL table, marked as no longer visible after an UPDATE or DELETE but not yet physically removed from disk.
DEFAULT PRIVILEGES
PostgreSQL mechanism that automatically defines privileges to assign to all future objects created in a schema, avoiding the need to repeat GRANTs manually.
default_statistics_target
The PostgreSQL parameter that controls the granularity of statistics collected by ANALYZE (size of MCV list and histogram).
Directive 2011/7/EU
European directive on late payments setting the standard term at 30 days, maximum at 60, and providing automatic late interest at the ECB rate + 8%.
Drill-down
Navigation in reports from an aggregated level to a detail level, typical of OLAP analysis and data warehouses.
DSO
Days Sales Outstanding — average number of days a company takes to collect its trade receivables. In Italy the average is 80 days...
E
ENUM (MySQL)
MySQL data type that allows a predefined set of string values, stored internally as a 1-2 byte numeric index.
ETL
Extract, Transform, Load — the process of extracting, transforming and loading data from source systems into the data warehouse.
Exchange Partition
An Oracle DDL operation that instantly swaps data segments between a non-partitioned table and a partition, without physically moving any data.
Execution Plan
The sequence of operations chosen by the database optimizer to resolve a SQL query.
F
Facilitator
Person responsible for guiding a meeting by maintaining focus, respecting the timebox, and ensuring everyone has a voice without the discussion degenerating.
Fact table
The central table in a star schema containing numeric measures and foreign keys to dimension tables.
Financial Float
Zero-cost liquidity generated by the difference between collection times from clients and payment times to suppliers, used as free working capital.
FLUSH PRIVILEGES
MySQL/MariaDB command that reloads grant tables from mysql.user, making manual privilege changes effective.
Folding Bike
Bicycle that folds in 10-20 seconds becoming a portable package for the office, metro or train, eliminating the problem of parking and theft.
Full Table Scan
A read operation where Oracle reads every block of a table from first to last, without using any index.
G
GIN Index
Generalized Inverted Index — PostgreSQL index type optimised for full-text search, trigram pattern matching and queries on arrays and JSONB.
GiST Index
Generalized Search Tree — PostgreSQL index family for data with geometric, range or similarity structure, indispensable for spatial and range queries.
Grain
The level of detail of a fact table in a data warehouse — the design decision that determines which questions the dimensional model can answer.
GRANT
SQL command to assign specific privileges to a user or role on databases, tables or columns. In MySQL 8 it no longer creates users implicitly.
Group Replication
MySQL's native mechanism for synchronous multi-node replication with automatic failover and quorum management.
GTID
Global Transaction Identifier — unique identifier assigned to every transaction in MySQL to simplify replication management.
H
Hash Join
Hash Join — a join strategy optimized for large data volumes, based on a hash table built in memory.
Hot Desk
Office space model where workstations are unassigned: whoever comes to the office takes an available desk.
Huge Pages
2 MB memory pages (instead of the standard 4 KB) that drastically reduce MMU and TLB pressure, improving Oracle performance on Linux.
I
I/O Scheduler
Linux kernel component that decides the order in which I/O requests are sent to disk, with direct impact on database performance.
information_schema
Read-only MySQL/MariaDB system schema exposing metadata about databases, tables, indexes, users and server state.
INTO OUTFILE
MySQL SQL clause that allows writing the result of a SELECT directly to a file on the server's filesystem.
Issue Tracker
Integrated tracking system for bugs, feature requests and project tasks. On GitHub, issues live in the same place as the code, ensuring complete traceability.
IST
Incremental State Transfer — Galera Cluster mechanism for transferring only missing transactions to a node rejoining the cluster.
K
Kimball
Ralph Kimball — data warehouse design methodology based on dimensional modeling, star schemas and bottom-up ETL processes.
Knowledge Transfer
Process of transferring knowledge between people, teams or systems, critical in IT projects where know-how loss can compromise operational continuity.
KPI
Key Performance Indicator — measurable metric that evaluates the effectiveness of an activity against a defined objective...
L
Late Payment Interest
Automatic interest prescribed by law (ECB rate + 8%) accruing on every invoice paid late, without the need for formal notice.
Least Privilege
Security principle that prescribes assigning to each user or process only the permissions strictly necessary to perform their function.
Lift-and-Shift
Migration strategy that moves a system from one environment to another without modifying its architecture, code, or configuration.
Local Index
Oracle index partitioned with the same key as the table, where each table partition has its corresponding index partition.
Lookup table
Reference table linked via foreign key that stores the valid values of an enumeration, along with any descriptive attributes.
M
MERGE
A SQL statement that combines INSERT and UPDATE in a single operation. In Oracle also known as upsert.
Micromanagement
Management style based on pointwise control of the team's daily activities. Causes motivation loss, turnover, and discourages initiative.
MVCC
Multi-Version Concurrency Control — PostgreSQL's concurrency model that maintains multiple row versions to ensure transactional isolation without exclusive...
mydumper
Open source logical backup tool for MySQL/MariaDB with true chunk-level parallelism, with parallel restore via myloader.
mysqlbinlog
MySQL command-line utility for reading, filtering and replaying the contents of binary log files.
mysqldump
Logical backup utility included in every MySQL installation, producing a sequential SQL file to recreate schema and data.
mysqlpump
Evolution of mysqldump introduced in MySQL 5.7 with table-level parallelism, deprecated by Oracle in MySQL 8.0.34.
N
Nested Loop
Nested Loop Join — the join strategy that scans the inner table for each row of the outer table, ideal for small datasets with an index.
NOLOGGING
Oracle mode that suppresses redo log generation during bulk operations (CTAS, INSERT APPEND, ALTER TABLE MOVE)...
O
Object Privilege
Oracle privilege that authorizes operations on a specific database object such as SELECT, INSERT, UPDATE or EXECUTE on a table, view or procedure.
OCI
Oracle Cloud Infrastructure — Oracle's cloud platform, offering significant licensing advantages for Oracle databases through the BYOL program.
OID (Object Identifier)
Internal numeric identifier used by PostgreSQL to refer to system objects (tables, types, functions). Unsigned 4-byte integer managed by the engine.
OLAP
Online Analytical Processing — processing oriented to multidimensional data analysis, typical of data warehouses.
Online DDL
MySQL/InnoDB mechanism that allows ALTER TABLE operations to run without blocking concurrent writes, with precise limits depending on the operation.
Oracle major release
Main version of the Oracle Database server with significant feature changes and dedicated Premier support cycle. Numbering: 19c, 21c, 23ai, 26ai.
Outcome vs Output
Distinction between what the team produces (output: code, documents, deliverables) and the final result measured by the business (outcome:
Outsourcing
Externalisation of IT activities or projects to external suppliers, with significant risks of know-how loss and vendor lock-in if not managed correctly.
P
Parking Lot
Visible list of topics that emerge during a meeting and deserve further discussion but are deferred to respect the timebox.
Partial Index
PostgreSQL index that covers only a subset of the table's rows, defined with WHERE in the CREATE INDEX. Reduces space and maintenance time.
Partita IVA
Italian tax regime for self-employed workers and freelancers, which in IT consulting implies directly bearing the credit risk toward clients.
Partition Pruning
Automatic Oracle mechanism that excludes irrelevant partitions during query execution, reading only partitions containing data matching the predicate.
Pedal Assist
Electric propulsion system that amplifies the cyclist's pedaling force, eliminating the problem of hills and sweat on urban home-to-work commutes.
pg_stat_statements
PostgreSQL extension that collects execution statistics for all SQL queries, an essential tool for performance diagnostics.
pg_stat_user_indexes
PostgreSQL system view that tracks how many times each index has been used by the planner — the primary tool for identifying useless indexes in production.
pg_trgm
PostgreSQL extension providing functions and operators for trigram-based similarity search, enabling GIN indexes for LIKE with wildcards.
PITR
Point-in-Time Recovery — a restore technique that allows bringing a database back to a precise moment in time, combining backups and transaction logs.
Pre-upgrade Assessment
Structured measurement of a database's size, growth rate, backup times and restore times before an upgrade.
Presenteeism
Organizational culture that equates physical office presence with productivity, regardless of results actually produced.
Psychological Safety
Team climate in which people can admit mistakes, say 'I don't know' and raise problems without fearing consequences to their professional standing.
Pull Request
Mechanism for proposing and reviewing code changes on platforms like GitHub. Enables code review, discussion and approval before merging into the main branch.
Q
Quorum
Majority-based consensus mechanism used in database clusters to prevent split-brain and ensure data consistency.
R
RAC
Real Application Clusters — Oracle technology that allows multiple instances to simultaneously access the same database...
Ragged hierarchy
A hierarchy where not all branches reach the same depth: some intermediate levels are missing.
Range Partitioning
A partitioning strategy that divides a table into segments based on value ranges of a column, typically a date.
Redo Log
Log files where Oracle records every data change before writing it to the datafiles, ensuring recovery in case of failure.
Relay log
Intermediate log file on a MySQL slave that receives events from the master's binary log before they are executed locally.
REVOKE
SQL command to remove privileges or roles previously granted to a user or role, complementary to the GRANT command.
RMAN
Recovery Manager — Oracle's tool for database backup, restore and recovery, including creation of standby databases for Data Guard.
ROI
Return on Investment — ratio between benefit obtained and cost incurred for an investment, often abused in AI sales pitches where promises exceed reality.
ROLE
PostgreSQL's fundamental entity that unifies the concept of user and permission group: a ROLE with LOGIN is a user, without LOGIN it is a privilege container.
RPO
Recovery Point Objective — the maximum amount of data an organisation can afford to lose in a disaster, measured in time.
RTO
Recovery Time Objective — the maximum acceptable time to restore a service after a failure or disaster.
RUP
Rational Unified Process. Iterative software development method released by Rational in 1998, organised in four phases (Inception, Elaboration, Construction, Transition).
S
SCAN Listener
Single Client Access Name — Oracle RAC component that provides a single access point to the cluster, distributing connections across available nodes.
SCD
Slowly Changing Dimension — a data warehouse technique for tracking changes over time in dimension tables.
Schema
Logical namespace within a database that groups tables, views, functions and other objects, enabling organization and permission separation.
Scope
Project perimeter that defines what is included and excluded: features, deliverables, constraints, and boundaries agreed with stakeholders.
Scope Creep
Uncontrolled expansion of project requirements beyond the initial scope, leading to delays, cost overruns and often project failure.
Scrum
Agile framework for project management that organizes work into fixed-length sprints, with defined roles (Product Owner, Scrum Master...
secure-file-priv
MySQL security directive that limits the directories where the server can read and write files, protecting the filesystem from unauthorised operations.
Self-parenting
A technique for balancing ragged hierarchies: an entity without a parent becomes its own parent.
Sequential Scan
Read operation where PostgreSQL reads all blocks of a table without using indexes, efficient on small tables but problematic on large ones.
SGA
System Global Area — Oracle Database's shared memory area containing buffer cache, shared pool, redo log buffer and other structures critical for performance.
shared_buffers
PostgreSQL's shared memory area serving as a cache for data blocks, the most important parameter for memory tuning.
Single-primary
MySQL Group Replication mode where only one node accepts writes while the others are read-only with automatic failover.
Smart Working
Flexible work model combining remote work and office presence, based on measurable objectives instead of schedules and physical presence.
Snapshot (Oracle)
A point-in-time capture of performance statistics taken periodically by AWR and used to generate comparative diagnostic reports.
Split-brain
Critical condition in a database cluster where two or more parts operate independently, accepting divergent writes on the same data.
SQL Domain
Construct introduced in Oracle Database 23ai that defines a reusable domain (base type + CHECK + DEFAULT + annotations) as a data dictionary object.
SQL Injection
Attack technique that inserts malicious SQL code into application inputs to manipulate queries executed by the database...
SST
State Snapshot Transfer — Galera Cluster mechanism for transferring a complete data copy to a node joining the cluster.
Stakeholder
Person or group with a direct interest in a project's outcome: client, end user, sponsor, technical team, or any party affected by project decisions.
Star schema
A data model typical of data warehouses: a central fact table connected to multiple dimension tables via foreign keys.
Surrogate key
A numeric identifier generated by the data warehouse, distinct from the source system's natural key. Essential for SCD Type 2.
Sustainable Mobility
Approach to urban transport that favors low environmental impact means — cycling, public transport, electric vehicles — reducing emissions, traffic, and costs.
Swappiness
Linux kernel parameter (vm.swappiness) controlling the system's propensity to move memory pages to swap...
Switchover
A planned Data Guard operation that reverses the roles between primary and standby without data loss, reversible and controlled.
System Privilege
Oracle privilege that authorizes global database operations such as CREATE TABLE, CREATE SESSION or ALTER SYSTEM, independent of any specific object.
systemd
Linux init system and service manager, used to manage multiple MySQL/MariaDB instances on the same server through separate unit files.
T
Tablespace
Logical storage unit in Oracle that groups one or more physical datafiles. Enables organising, managing and optimising disk space for tables...
THP
Transparent Huge Pages — Linux kernel feature that automatically promotes normal pages to huge pages...
Three Amigos
Nickname given to Grady Booch, James Rumbaugh and Ivar Jacobson, the three creators of UML who worked at Rational Software between 1994 and 1998.
Timeboxing
Time management technique that assigns a fixed, non-negotiable interval to an activity, forcing conclusion within the established limit.
Transport Lag
The delay in transmitting redo logs from the primary database to the standby in a Data Guard configuration. A critical indicator of replication health.
Type safety
Property of a type system that prevents, at parse-time, the use of values incompatible with the declared type of a column, parameter or variable.
U
UML
Unified Modeling Language. Standard object-oriented modeling language, adopted by OMG in November 1997 from the merger of three previous methods.
Unified Audit
Centralized auditing system introduced in Oracle 12c that unifies all audit types into a single infrastructure, replacing the legacy traditional audit.
Unix Socket
Local inter-process communication mechanism on Unix/Linux systems, used by MySQL for faster connections than TCP when client and server are on the same host.
Use Case
Requirements analysis technique introduced by Ivar Jacobson that describes the system from the point of view of the actor who uses it, not from the objects that compose it.
V
VACUUM
PostgreSQL command that reclaims space occupied by dead tuples, making it reusable for new inserts without returning it to the operating system.
VALIDATE / NOVALIDATE
Oracle modes for applying a constraint at creation or modification time: VALIDATE checks all existing rows, NOVALIDATE skips the check.
Vendor Lock-in
Structural dependency on an external supplier that makes switching providers difficult or costly, often caused by loss of know-how and code ownership.
Version Control
System that tracks every change to source code, enabling history viewing, reverting changes and collaborating without overwrites. Git is the current standard.
W
Wait Event
A diagnostic event recorded by Oracle whenever a session cannot proceed and must wait for a resource — I/O, lock, network or CPU.
WSREP
Write Set Replication — synchronous replication API and protocol used by Galera Cluster to keep cluster nodes aligned in real time.
X
xtrabackup
Hot physical backup tool for MySQL/MariaDB developed by Percona. Copies InnoDB files with the database running...
Y
Yes-And
Communication technique from improvisational theatre that replaces 'No, but...' with 'Yes, and...', turning discussions into collaborative building.
Z
ZDM
Zero Downtime Migration — Oracle's tool for automating migrations to OCI by combining Data Guard and Data Pump under an orchestration layer.