It is not possible for a purchaser to postpone sourcing of few requirements in Sourcing Cockpit (SOCO).
There is an option in Sourcing Cockpit to postpone sourcing of few requirements for a certain time frame. The requirements will appear back in Sourcing Cockpit after the given time duration.
It is also possible to display all the deferred items by using the Show Deferred items check box.
Following highlighted fields are introduced in SOCO, Select Requisition screen for this feature:
To use the feature, you have to first activate the Business Function SRM_CONT_IMPR_3 and then activate the Customizing switch Defer Sourcing(SRM_703_SOCO_RESUBMISSION) under SRM Server-> Sourcing->Activate/Deactivate Defer Sourcing.
Link to the video: https://www.youtube.com/watch?v=3g-RXPaW0tU
For complete details about SAP SRM 7.03 refer: SAP SRM 7.03