How to achieve sequence of Insert operation
i.e.Insert#2 should not be performed until Insert#1 completed.

When user have requirement to perform Insert operation in particular sequence to assure
business requirement of sequence of Insert statement.
e.g. If we have Insert in Table A further calling Insert in Table B and maintain the
sequence of activity where Insert A should finish first then Insert B and further on.

We can use Trigger with AFTER INSERT option.
https://www.ibm.com/support/knowledgecenter/SSEPGG_10.5.0/com.ibm.db2.luw.admin.dbobj.doc/doc/t0020229.html

If we have multiple Insert in Store procedure  The operation will be called sequentially
but they do not wait until one operation finish to call next one.

So best way to achieve sequence of insert would be through Trigger with After INSERT operation.