SA Schedule Lines from MD03 date calculation

[Former Member]

Hi

Please find the following snap from MD03 ,

here the schedule lines generated dt 06-06-14, for this material planned delivery time and GR processing time is zero in material master,

In info record planned delivery time is 1 day, I unable to understand why system generated the schedule after 4 days

Then I created new material copying the above material and done MD03 for newly created then the schedule lines generated on 02-06-14, Why the system proposes two different schedule dates for new material and ol material?

I searched the forum and checked all the available configurations and finally found

IMG-Production-MRP-Planning-scheduling and capacity parameters-Parameters for determining the basic date

when i checked the box for Start in past and again run the MD03 for the same material, then the results as follows, which is correct i think as per MMR

Though i got the required results but did not understand what is this field Start in Past does? how the calculations takes place, what will be the effect if i keep this checked ?

Thanks

[Petepall · Accepted solution]

Do you have a planned delivery time or GR processing time in the scheduling agreement itself?

Please check in the additional details at item level what is maintained there.

[Former Member · Accepted solution]

Thanks Peter, you were right,

SA have the details of GR processing time and the planned delivery time,

But how these fields were populated?? I think at the time of creation of SA, material master has the data and it has been carried forward, is it right

But How this Parameters for determining the basic date work ?

[Petepall · Accepted solution]

But how these fields were populated?? I think at the time of creation of SA, material master has the data and it has been carried forward, is it right

Either a user manually maintained the values that you have in the SA or these values where at time of creation present in either the material master or the info record.

The system (depending on the config set-up) copies the values in the following sequence to the SA.

1. If values are maintained in the info record the system will adopt the data from the info record
2. If no values in the info record then the system will copy the data from the material master record.

I can't judge from here what values where maintained where. You can check the change logs to check if you can find the values back. In case you can not find the values in the change logs then it's likely that the values where manually maintained in the SA.

But How this Parameters for determining the basic date work ?

The determination of the date works based on the backward and forward scheduling.

The system will first schedule using backward scheduling if this is not possible then forward scheduling is used.

Some explanation on backward and forward scheduling.

Backward scheduling explained

When scheduling materials in SAP MRP, the system will first try to backward schedule the materials.

With backward scheduling is meant that the SAP MRP system will start to count backward from the

requirement date and will then determine the delivery date. As long as this date is later then the current

date, the delivery date will be determined without a problem.

Below image shows a graphical representation of backward scheduling.

Forward scheduling explained

Forward scheduling is used by the SAP MRP system when the date determined by the backward

scheduling process is lying before the actual date. The forward scheduled date is determined by taking

today’s date and then adding all the relevant processing time to determine the possible delivery date.

This kind of scheduling will throw an exception message in the MRP view screen (MD04 / MD06 /

MD07). These exception messages are telling the materials expeditor that action from her/his part is

required in order to either postpone the production of the finished good or to work with the vendor to

pull forward the required materials.

Below image shows a graphical representation of how the forward scheduling is performed by SAP.

[Former Member · Accepted solution]

Thanks Peter, Very nicely explained,

could you please throw some light on the system behavior when i checked the box Start in past,

Please refer the last snap of my post

IMG-Production-MRP-Planning-scheduling and capacity parameters-Parameters for determining the basic date

when i checked the box for Start in past and again run the MD03 for the same material, then the results as follows, which is correct i think as per MMR

[Petepall · Accepted solution]

Basically when you activate this setting it does as the function say and the result of the lead time calculation is that it can calculate into the past. In other words you deactivate the forward scheduling.