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Using CreateDB to generate an indexable length of UDT's in a DB during runtime (S7-1500)

Created by: Matt Norris at: 11/1/2018 2:36 PM (7 Replies)

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11/1/2018 2:36 PM	Rate (0)
Matt Norris Member Joined: 8/1/2016 Last visit: 8/21/2025 Posts: 5 Rating: (0)	Dear Guru's I am looking, if possible, for a solution to generating DB's at run time where the DB to be generated contains a variable defined array length of UDT's. For example, a variable called 'INT_Length' is contained in a global DB. INT_Length can be changed during run time (for example we will give it the value of '10') INT_Length is then used to generate (create_db) a DB during run time which contained 10 copies of a UDT. I understand that you can not generate array indexes at run time due to a limitation with S7, also the length is not known at compile time so I can not hard code the length of an array. Hence attempting to use the create_db as a work around. There are several DB's to be created using a different UDT for each all of which are unknown 'lengths' Note that a DB is constrained to a single UDT, that meaning a single DB wont contain more than one type of UDT. I have considered 'over-indexing' arrays so they are larger than the possible lengths however i don't know what the maximum size of length is going to be plus it seams to me to be rather a lot of wasted memory. After that i will create an index (in predefined global DB at compile time) of the various generated DB's numbers so that I can pass those numbers to ANY_DB and use a FB with ANY_DB_TO_VARIANT in order to access, process and save data in said DB's. However, baby steps first... and i first must try to understand if it is at all possible to use the create_db method to achieve the results I would like? CPU: 1513-PN (Version 2.1) TIA Portal: V14 SP1 Preferred Language: SCL I can also consider migrating to V15 if a suitable solution exists there that is not available in V14. I thank you for your patience and time to any suggestions you might have in advance and hope that my above explanation is understandable.
	Last edited by: Matt Norris at: 11/1/2018 2:38:42 PM Last edited by: Matt Norris at: 11/1/2018 2:41:08 PM
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11/1/2018 4:24 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/3/2025 Posts: 16057 Rating: (2513)	Using search (google) with phrase: "site:siemens.com tia portal s7-1500 create_db", maybe this link from those results will help: https://support.industry.siemens.com/tf/WW/en/posts/create-db-entries-from-function/167758 https://support.industry.siemens.com/tf/WW/en/posts/create-an-array-with-fixed-length-in-run-time-in-step7-v15/197494 http://bfy.tw/KeJ9 Matt Norris Dear Guru's I am looking, if possible, for a solution to generating DB's at run time where the DB to be generated contains a variable defined array length of UDT's. For example, a variable called 'INT_Length' is contained in a global DB. INT_Length can be changed during run time (for example we will give it the value of '10') INT_Length is then used to generate (create_db) a DB during run time which contained 10 copies of a UDT. I understand that you can not generate array indexes at run time due to a limitation with S7, also the length is not known at compile time so I can not hard code the length of an array. Hence attempting to use the create_db as a work around. There are several DB's to be created using a different UDT for each all of which are unknown 'lengths' Note that a DB is constrained to a single UDT, that meaning a single DB wont contain more than one type of UDT. I have considered 'over-indexing' arrays so they are larger than the possible lengths however i don't know what the maximum size of length is going to be plus it seams to me to be rather a lot of wasted memory. After that i will create an index (in predefined global DB at compile time) of the various generated DB's numbers so that I can pass those numbers to ANY_DB and use a FB with ANY_DB_TO_VARIANT in order to access, process and save data in said DB's. However, baby steps first... and i first must try to understand if it is at all possible to use the create_db method to achieve the results I would like? CPU: 1513-PN (Version 2.1) TIA Portal: V14 SP1 Preferred Language: SCL I can also consider migrating to V15 if a suitable solution exists there that is not available in V14. I thank you for your patience and time to any suggestions you might have in advance and hope that my above explanation is understandable.
	Last edited by: 0_Einstein at: 11/20/2023 13:59:51 updated 3rd URL science guy
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11/1/2018 5:05 PM	Rate (0)
Matt Norris Member Joined: 8/1/2016 Last visit: 8/21/2025 Posts: 5 Rating: (0)	huggy_d1 Using search (google) with phrase: "site:siemens.com tia portal s7-1500 create_db", maybe this link from those results will help: https://support.industry.siemens.com/tf/WW/en/posts/create-db-entries-from-function/167758 https://support.industry.siemens.com/tf/WW/en/posts/create-an-array-with-fixed-length-in-run-time-in-step7-v15/197494 http://bfy.tw/KeJ9 Matt Norris Dear Guru's I am looking, if possible, for a solution to generating DB's at run time where the DB to be generated contains a variable defined array length of UDT's. For example, a variable called 'INT_Length' is contained in a global DB. INT_Length can be changed during run time (for example we will give it the value of '10') INT_Length is then used to generate (create_db) a DB during run time which contained 10 copies of a UDT. I understand that you can not generate array indexes at run time due to a limitation with S7, also the length is not known at compile time so I can not hard code the length of an array. Hence attempting to use the create_db as a work around. There are several DB's to be created using a different UDT for each all of which are unknown 'lengths' Note that a DB is constrained to a single UDT, that meaning a single DB wont contain more than one type of UDT. I have considered 'over-indexing' arrays so they are larger than the possible lengths however i don't know what the maximum size of length is going to be plus it seams to me to be rather a lot of wasted memory. After that i will create an index (in predefined global DB at compile time) of the various generated DB's numbers so that I can pass those numbers to ANY_DB and use a FB with ANY_DB_TO_VARIANT in order to access, process and save data in said DB's. However, baby steps first... and i first must try to understand if it is at all possible to use the create_db method to achieve the results I would like? CPU: 1513-PN (Version 2.1) TIA Portal: V14 SP1 Preferred Language: SCL I can also consider migrating to V15 if a suitable solution exists there that is not available in V14. I thank you for your patience and time to any suggestions you might have in advance and hope that my above explanation is understandable. Thank you for the response huggy_d1, I had actually already extensively searched the Siemens site include some very insightful posts that you yourself had made, some of which actually pushed me toward this method in the first place. Since you have categorically stated in your second link that when 'simulating' a dynamic array is bad because a firmware update can break it, ill consider the method a no go. Regards,
	Last edited by: Matt Norris at: 11/1/2018 5:06:50 PM
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11/1/2018 5:13 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/3/2025 Posts: 16057 Rating: (2513)	I applaud your decision If you use a one-size-larger memory card and store your oversized DBs there and only pull them into use as required, you can store a large array of UDT data records using optimized DBs. Of course, if you find your project leaves you with plenty of available work memory to store everything there, there is even less work to do in real-time on the PLC because everything is available all the time.
	science guy
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11/1/2018 5:14 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 9/3/2025 Posts: 16057 Rating: (2513)	Hopefully you smiled or laughed at the 3rd link. I had no way to know you had already dug into the "interwebs"
	science guy
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11/1/2018 5:30 PM	Rate (0)
Matt Norris Member Joined: 8/1/2016 Last visit: 8/21/2025 Posts: 5 Rating: (0)	I had a strong suspicion that was going to be the case and its a perfectly viable solution, luckily I have a 256MB card to use for testing . Thanks again for your help, and no worries on the 3rd link.
	Last edited by: Matt Norris at: 11/1/2018 5:31:37 PM Last edited by: Matt Norris at: 11/1/2018 5:31:54 PM
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11/20/2023 4:37 AM	Rate (0)
Sai Teja Regular Member Joined: 3/6/2019 Last visit: 6/11/2025 Posts: 12 Rating: (0)	0_Einstein Hopefully you smiled or laughed at the 3rd link. I had no way to know you had already dug into the "interwebs" 3rd link is not working

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11/21/2023 6:06 AM	Rate (0)
Transponder Snail Member Joined: 6/27/2017 Last visit: 6/26/2024 Posts: 158 Rating: (21)	Sai Teja 0_Einstein Hopefully you smiled or laughed at the 3rd link. I had no way to know you had already dug into the "interwebs" 3rd link is not working Hello Sai, the third link is just a reference to google ("let me google that for you")

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