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PersistenceTime

is an option for various functions that specifies when a persistent value should be treated as expired.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Properties & Relations  
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PersistenceTime

PersistenceTime

is an option for various functions that specifies when a persistent value should be treated as expired.

Details

  • PersistenceTime can be used for PersistentSymbol and InitializationValue.
  • Values can be given as relative times in seconds or relative date and time specifications.
  • Values are typically converted to absolute times based on the current time.
  • The value Infinity () can be used to specify that a persistent value should never expire.
  • An expired persistent value is treated as nonexistent, and the underlying persistent object may be removed.

Examples

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Basic Examples  (1)

Define a persistent value that expires in 5 seconds:

Wolfram Language code: PersistentSymbol["x", PersistenceTime -> 5] = 1;

After 5 seconds, it is no longer used:

Wolfram Language code: PersistentSymbol["x"] Pause[5];PersistentSymbol["x"]

Scope  (2)

Define a persistent value that expires in 1 minute:

Wolfram Language code: PersistentSymbol["x", PersistenceTime -> Quantity[1, "Minutes"]] = 1;

Numbers are treated as seconds:

Wolfram Language code: PersistentSymbol["x", PersistenceTime -> 5] = 1;

Define a persistent value that expires in 5 days:

Wolfram Language code: PersistentSymbol["x", PersistenceTime -> ["5days"]] = 1;

A persistence time of Infinity causes the value to never expire:

Wolfram Language code: PersistentSymbol["Eternal", PersistenceTime -> ∞] = 1;
Wolfram Language code: PersistentObject["Eternal", $PersistenceBase]["ExpirationDate"]

Properties & Relations  (2)

Values specified with PersistenceTime are converted to absolute expiration dates:

Wolfram Language code: PersistentSymbol["x", "KernelSession", PersistenceTime -> 5] = 1;
Wolfram Language code: PersistentObject["x", "KernelSession"]["ExpirationDate"]

The default setting for PersistenceTime is to never expire:

Wolfram Language code: PersistentSymbol["Eternal"] = 42;
Wolfram Language code: PersistentObject["Eternal", $PersistenceBase]["ExpirationDate"]
Wolfram Research (2017), PersistenceTime, Wolfram Language function, https://reference.wolfram.com/language/ref/PersistenceTime.html.

Text

Wolfram Research (2017), PersistenceTime, Wolfram Language function, https://reference.wolfram.com/language/ref/PersistenceTime.html.

CMS

Wolfram Language. 2017. "PersistenceTime." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/PersistenceTime.html.

APA

Wolfram Language. (2017). PersistenceTime. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/PersistenceTime.html

BibTeX

@misc{reference.wolfram_2026_persistencetime, author="Wolfram Research", title="{PersistenceTime}", year="2017", howpublished="\url{https://reference.wolfram.com/language/ref/PersistenceTime.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_persistencetime, organization={Wolfram Research}, title={PersistenceTime}, year={2017}, url={https://reference.wolfram.com/language/ref/PersistenceTime.html}, note=[Accessed: 12-June-2026]}