Northern railways has cancelled some trains due to farmers' agitation in Punjab against farm bills and some trains have been terminated for short period. Some of the trains have also been diverted.
Here is the list of trains which have been affected due to the agitation:

CANCELLED
02425/02426 New Delhi- Jammutawi-New Delhi Rajdhani Express special train journey (commencing from October 19 to 20)
22439/22440 New Delhi- Shri Mata Vaishno Devi Katra- New Delhi Vande Bharat Express train journey (commencing on October 19)
02461 New Delhi- Shri Mata Vaishno Devi Katra Express special train journey (commencing from October 20 to 21) 
02462 Shri Mata Vaishno Devi Katra- NewDelhi Express special train journey (commencing from October 19 to 20)
02011/ 02012 New Delhi- Kalka - New Delhi Shatabdi Express special train journey and the 02029/ 02030 New Delhi- Amritsar - New Delhi Shatabdi Express special train (commencing from October 19 to 20).
02054/ 02053Haridwar - Amritsar - Haridwar Jan Shatabdi Express special train journey (commencing from October 20 to 21) 
02422 Jammutawi-Ajmer Express special train journey commencing on October 20 has been cancelled while the 02421 Ajmer - Jammutawi Express special train journey commencing on October 21 has also been cancelled.
02231 Lucknow-Chandigarh Express special train journey (commencing on October 20)
02232 Chandigarh-Lucknow Express special train journey (commencing on October 21)
04887 Barmer - Rishikesh Express special train journey (commencing on October 20)
04888 Rishikesh-Barmer Express special train journey (commencing on October 21)
04519/ 04520 Delhi -Bhatinda -Delhi Express special train and the 02471/ 02472 Sriganganagar- Delhi -Sriganganagar Express special train (commencing on October 20)

 SHORT PERIOD TERMINATION
02903 Mumbai Central- Amritsar Express train journey (commencing from October 17 to 18) short terminated at Ambala.
02904 Amritsar- Mumbai Central Express train journey (commencing from October 19 to 20) has been short originated from Ambala, partially cancelled between Ambala - Amritsar-Ambala.
02925 Bandra Terminus- Amritsar Express train journey (commencing from October 18 to 19) short terminated at Ambala.
02926 Amritsar- Bandra Terminus Express train journey (commencing from October 20 to 21) have been short originated from Ambala, partially cancelled between Ambala - Amritsar- Ambala.
02715 Nanded - Amritsar Express train journey (commencing from October 18 to 19) short terminated at New Delhi.
02716 Amritsar-Nanded Express train journey (commencing from October 20 to 21) short originate from New Delhi, partially cancelled between New Delhi- Amritsar-New Delhi
03307 Dhanbad -Ferozpur Express train journey (commencing from October 17 to 18) short terminated at Ambala.
03308 Ferozpur- Dhanbad Express train journey commencing from October 19 to 29 short originated from Ambala, partially cancelled between Ambala-Ferozpur-Ambala.
04649 Jaynagar - Amritsar Express train journey (commencing October 18) short terminated at Ambala.
04650 Amritsar-Jaynagar Express special train journey (commencing on October 19 and 21) short originate from Ambala, partially cancelled between Amritsar-Ambala.
04673 Jaynagar-Amritsar Express special train journey (commencing on October 19) short terminated at Ambala.
04674 Amritsar-Jaynagar Express train journey (commencing on October 20) short originated from Ambala, partially cancelled between Amritsar-Ambala.
02057 NewDelhi- Una Himachal Express train journey (commencing from October 19 and 20) short terminated at Ambala.
02058 Una Himachal -NewDelhi Express train journey (commencing from October 20 to 21) short originated from Ambala, partially cancelled between Ambala- Una Himchal -Ambala.
04651 Jaynagar - Amritsar Express special train journey (commencing on October 20) short terminated at Delhi.
04652 Amritsar-Jaynagar Express special train journey (commencing on October 21) short originated from Delhi, partially cancelled between Delhi and Amritsar.
02357Kolkata - Amritsar Express special train journey (commencing on October 20) short terminated at Ambala.
02358 Amritsar-Kolkata Express special train journey (commencing on October 22) short originated from Ambala, partially cancelled between Ambala and Amritsar.
04654 Amritsar - Newjalpaiguri Express special train journey (commencing on October 21) short originated from Saharanpur, partially cancelled between Saharanpur and Amritsar.
09025 Bandra Terminus - Amritsar Express special train journey (commencing on October 19) short terminated at Ambala
09026 Amritsar - Bandra Terminus Express special train journey (commencing on October 21) short originated from Ambala, partially cancelled between Ambala and Amritsar.
02237 Varanasi -Jammutawi Express special train journey (commencing on October 20) short terminated at Saharanpur. 
02238 Jammutawi - Varanasi Express special train journey (commencing on October 21) short originated from Saharanpur, partially cancelled between Saharanpur and Jammutawi.
04131 Prayag -Udhampur Express special train journey (commencing on October 20) short terminated at Saharanpur
04132 Udhampur - Prayag Express special train journey (commencing on October 21) short originated from Saharanpur, partially cancelled between Saharanpur and Jammutawi.
02355 Patna -Jammutawi Express special train journey (commencing on October 20) short terminated at Bareilly
02356 Jammutawi - Patna Express special train journeys (commencing on October 21) short originated from Bareilly, partially cancelled between Bareilly and Jammutawi.
00901 Bandra Terminus - Jammutawi parcel Express special train journey (commencing on October 18) short terminated at Ambala
00902 Jammutawi - Bandra Terminus parcel Express special train journeys (commencing on October 20) short originated from Ambala, partially cancelled between Ambala and Jammutawi.

TRAINS DIVERTED
The 00468 Amritsar-Howrah Express special train journey (commencing on October 19) short originated from Delhi, partially cancelled between Delhi and Amritsar.

05910 Lalgarh- Dibrugarh Express train journey (commencing from October 19 to 20) diverted to run via Hanumangarh-Hisar-Bhiwani- Rohtak.

(media reports)