# Default sequence in UVM

**URL:** <https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013>\
**Category:** UVM\
**Tags:** UVM, default\_sequence, sequence\
**Created:** [August 30, 2020, 6:23am UTC](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013 "2020-08-30T06:23:24Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Malai\_21](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/m/d78d45/32.png) [@Malai\_21](https://verificationacademy.com/forums/u/Malai_21)\
**Post date:** [August 30, 2020, 6:23am UTC](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/1 "2020-08-30T06:23:24Z")

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Hello all,  
In UVM, default sequences can be used to start a sequence. I can see many replies in this forum regarding default sequences say “It is not recommended to use default sequences in test”.  
Could you please tell why it is not recommended to use default sequences in a test?  
what will the issue while using a default sequence?

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**Author:** ![cgales](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/c/ccd318/32.png) [@cgales](https://verificationacademy.com/forums/u/cgales)\
**Post date:** [August 30, 2020, 11:36am UTC](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/2 "2020-08-30T11:36:31Z")

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_In reply to [SriGanesh D](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013):_

In general, you want all of the testbench stimulus generation and response (i.e. sequences) to be configured/started during the run\_phase() of your test. This is desired to allow the user to control the exact relationship between these sequences.

There are several reasons using a default\_sequence doesn’t follow this:

- Setting a default\_sequence is done outside of the run\_phase(). Additionally, changing the default\_sequence requires changes outside of the run\_phase().
- There is no mechanism to control when the default\_sequence starts, other than at the beginning of a specific phase.
- You can’t run more than one sequence
- You can’t easily run additional sequences on the same sequencer
- Debugging a default\_sequence can be difficult since the user may not be aware that the default\_sequence exists.
- The default\_sequence can’t be randomized() or otherwise configured

It’s simple enough to create()/randomize()/start() a single sequence at the beginning of the run\_phase() instead of setting a default\_sequence.

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**Author:** ![ansami](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/a/5e9695/32.png) [@ansami](https://verificationacademy.com/forums/u/ansami)\
**Post date:** [October 13, 2021, 6:57am UTC](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/3 "2021-10-13T06:57:52Z")

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_In reply to [cgales](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/2):_

Agree with your reply, but i am wandering what is the advantage by using `default_sequence` and has got no idea. do you have any idea or advice ?

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**Author:** ![chr\_sue](https://verificationacademy.com/forums/user_avatar/verificationacademy.com/chr_sue/32/1199_2.png) [@chr\_sue](https://verificationacademy.com/forums/u/chr_sue)\
**Post date:** [October 13, 2021, 8:05am UTC](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/4 "2021-10-13T08:05:26Z")

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_In reply to [ansami](https://verificationacademy.com/forums/t/default-sequence-in-uvm/38013/3):_

The default\_sequence is a leftover from the OVM which is not deprecated. There is no benefit using this construct. You should not use it in your environment.