Scenario:
Oracle Recipe Tool / Microservices
JNDI : jdbc/SOAXAOPS
PLSQL : schema.pkg1.procedure

This is the entry point to an on-premise DB package.
It can be called from cloud and non-cloud services.

Now whenever I would compile schema.pkg1
The callback will give below error :
ORA-04065: not executed, altered or dropped package body "schema.pkg1"
ORA-06508: PL/SQL: could not find program unit being called: "schema.pkg1"

This error can be bypassed if a DDL was issued in this schema or existing stale connections are explicitly killed.

So I added PRAGMA SERIALLY_REUSABLE; to schema.pkg1 based on below url
========================================================================
https://stackoverflow.com/questions/1761595/frequent-error-in-oracle-ora-04068-existing-state-of-packages-has-been-discarde
https://docs.oracle.com/en/cloud/paas/integration-cloud/database-adapter/resolve-error-ora-04068-existing-state-packages-has-been-discarded.html
https://docs.oracle.com/cd/E11882_01/appdev.112/e25519/packages.htm#LNPLS99977

In addition integrations team did this modification:
Under Connection Properties:
Test Connections on Reserve: Yes
Test Table Name:
SQL begin
dbms_session.modify_package_state(dbms_session.reinitialize);
end;
Seconds to trust Idle Pool Connection: 0

This solved initial error of ORA-04065 , ORA-06508
However it gave 1-off error : ORA-06508: PL/SQL: could not find program unit being called
This was at the line in schema.pkg1 which was giving call to schema.pkg2
Now schema.pkg2 is not having PRAGMA SERIALLY_REUSABLE;

In a request set of 2 requests... first one faced this err and subsequent requests have been fine so far... (This is UAT environment)

==============
Question is :
==============
When I recompile pkg (HOT patch) in UAT can it re happen.
Do I need to add this pragma to all nested packages.
What are the pros and cons of using this Pragma apart from trigger and SQl prompt usage as mentioned on Oracle documentation.
Is there an alternate way to deal with these errors for callback services.

CREATE OR REPLACE PACKAGE pkg IS
  n NUMBER := 5;
END pkg;
/

CREATE OR REPLACE PACKAGE sr_pkg IS
  PRAGMA SERIALLY_REUSABLE;
  n NUMBER := 5;
END sr_pkg;
/

BEGIN
  pkg.n := 10;
  sr_pkg.n := 10;
END;
/

BEGIN
  DBMS_OUTPUT.PUT_LINE('pkg.n: ' || pkg.n);
  DBMS_OUTPUT.PUT_LINE('sr_pkg.n: ' || sr_pkg.n);
END;
/

pkg.n: 10
sr_pkg.n: 5