Retention policy

As explained in 100 SQL Server Mistakes and How to Avoid Them

A data retention policy specifies how long stored data must be preserved before it may be deleted or archived.

A retention policy specifies how long stored data must remain available before deletion or archiving. Treating it as a paperwork detail can turn ordinary growth into a storage crisis. section 9.6

Mistake: sizing storage without retention

MarketingArchive receives 5 GB of data daily and retains it for three years. A database that appears to have 50 GB free can grow to about 1.78 TB after one year; adding TempDB, the transaction log, and safety headroom may require roughly 3.2 TB. If the SAN has only 2 TB available, the result can be a business dispute and extended downtime while new capacity is installed. section 9.6

Use the policy as an operational input:

• Calculate required data-file capacity from the daily ingestion rate and retention period. section 9.6
• Include TempDB, the transaction log, unexpected growth, and existing SAN commitments in the estimate. section 9.6
• Apply an appropriate retention policy to backups, and keep backups air-gapped or on immutable storage; encrypt them against cyberattacks. section 12.12

Figure 9.5 Linear growth pattern

Use the linear-growth figure to visualize how a steady daily intake accumulates against the retention horizon. section 9.6

How 100 SQL Server Mistakes and How to Avoid Them covers it

How deep it goes

Calculates linear data growth and associated storage needs, but stops short of defining deletion or archival procedures.

Examples

Illustrates retention through MarketingArchive, 5 GB daily ingestion, three-year retention, and air-gapped or immutable backups.

What you can do after

Evaluate storage forecasts and backup safeguards using retention duration, growth rate, headroom, and protection requirements.

How it connects

Connects retention policy with capacity planning, data growth, TempDB, transaction logs, backups, and ransomware protection.

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Also explained in

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  Architecting an Apache Iceberg LakehouseA retention policy specifies how long table states and associated files or metadata may be retained before expiration or deletion.
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  Kafka for ArchitectsA retention policy is a rule governing how long or under what conditions stored Kafka records remain available.
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  MongoDB 8.0 in Action, Third EditionA retention policy defines how long backup copies or recovery data are preserved.
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  Effective Data AnalysisA data retention policy specifies how long data may be kept and the conditions under which it must be anonymized or deleted.
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  Apache Kafka in ActionA retention period is the duration for which Kafka retains records before allowing them to be deleted.
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  Just Use Postgres!A data retention policy is a rule that automatically removes time-series chunks containing data older than a specified age.
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  Elasticsearch in Action, Second EditionA snapshot retention policy specifies the conditions and duration governing how long snapshots remain available.
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  Think Like a CTOA retention policy specifies how long data must be kept and when or how it may be deleted or archived.
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  Build AI-Enhanced Web AppsA retention policy specifies how long stored backups or other records are preserved before deletion.

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Related concepts

• training datasetconfigures · A collection of examples or observations supplied to a learning procedure to fit or adapt a model or learn its patterns or parameters.
• logconfigures · A log is a record of events, activity, or diagnostic information produced during the operation of a system or process, often ordered by time.
• GDPRconfigured by · The General Data Protection Regulation (GDPR) is a European Union regulation governing the processing of personal data and protecting individuals’ rights concerning that data.
• signalconfigures · A signal is an observable value, event, or pattern that conveys information about a condition, state, or phenomenon.

This explainer was generated by Manning's knowledge graph from the text of 100 SQL Server Mistakes and How to Avoid Them. The section links point to the parts of the book it draws on.