Warning: This selection will block the complete version '&1'

What causes this issue?

This selection will block the complete version '&V1&'. As long as this
block exists, no other user can change data in this version.

System Response

If you have selected too many objects, the system can no longer attach
blocks to individual objects and so is forced to block the entire
version.

How to fix this error?

If possible, reduce the number of selected objects by adjusting the
selection in the selector. If you are not planning to change data, then
you should switch to display mode. No blocks are set in display mode.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.