Deleting Early Start Constraints

Not sure it can be done in global change. Quick fix if you have a lot of constraints is to export act ID and constraints data to excel and manually delete the records in excel then import back into P3.
Make a copy of project 1st, no undo with import/export.

For the import/export, find here after the structure of an excel file:
ACT ECON ECOND LCON LCOND CON COND
AA1010 XF 16/10/2002
AA3020 HA
AA3090 ON 11/08/2004 ON 11/08/2004
AA3120 EF 30/06/2004
AA3185 HA
AA3190 XF 10/05/2004
AA3280 XF 14/05/2004
AA4285 HA
AA5051 ZT
AA5684 ES 18/08/2003
AA5686 ES 06/02/2004
AAAAAA7950 MF 15/10/2004
AAAAAB2000 MS 07/07/2004
AAAAAB2001 MS 07/07/2004
It is not easy to read the first time.
ECON mean early constrain type
ECOND used to insert the early date to constrain
LCON mean late constrain type
LCOND used to insert the late date to constrain
CON other date constrain, like expected and mandatory
COND used to insert the data

Then
ES/LS: Ealry/late start
EF/LF: Early/late finish
XF: expected finish
ON: start on
ZF: zero float
MF: must finish on
MS: must start on
and so on.

A lot easier to just the functions already provided by P3.

In Glaobal Change, enter in the Then section

SNE EQ " ", this will remove all early start constraints,

SNL for late start and so on.

HTH