Causes of invalidated package

Question

Hi,
I've found on the forums some information about why a package could become invalidated.
We are encountering the 'ORA-04068: existing state of packages has been discarded' error (see stack trace at the bottom of this message).
We get this error at random (not at a specific moment in time). And always with the same package.
I found on the forums that a cause could be:
- a view, used in the package, that gets renamed (this is not the case).
- package level variables (I can not check this myself. Our client, who runs the Oracle instance, is doing that now).
1. Are there any other causes of a package becomming invalid?
2. Related: does a synonym become invalid when it's underlying package is invalid, or can a synonym be invalid, while it's underlying package is not?
3. Can our client, who is reluctant in accepting the fact that the problem lies with their Oracle database (i.e. packages being invalidated), check the exact reason of the invalidation in more detail (logs, ...)?
Thanks in advance for any insights,
Vincent
Stack:
ORA-04068: existing state of packages has been discarded
ORA-04061: existing state of package body "MYCLIENT.THEPACKAGE" has been invalidated
ORA-04065: not executed, altered or dropped package body "MYCLIENT.THEPACKAGE"
ORA-06508: PL/SQL: could not find program unit being called
ORA-06512: at line 1

Answer 1

Packages become invalidated when any database object (table, view etc.) that that package has dependecies on is altered in any way.
When a Package is being used it is loaded into memory and a "session state" is created for that package. This session state holds all of the package level variables for that session (different sessions running the same package will have their own copy of the package variables). If a dependency object is altered then the package is invalidated automatically by Oracle. If the package doesn't have any package level variables then Oracle will automatically recompile the package when the next call is made to anything within it by the session in question, but if variables exist then Oracle determines that these variables are now out of date because of the need for it to recompile the package. Because of this it has to discard the session state, which is why you get the error saying that the state has been discarded.
One way to get around this is to not have any package level variables.
If you need to have some variables (constants and types too) that are accessible by many procs/fns inside your package then a way to do this is to create another package spec containing these variables and alter the package to reference them in that package. That way, the package that has the dependencies and needs recompiling can do so without having any "state" to worry about being discarded and the variables in the other package are just variables and don't have any dependencies so that other package doesn't get invalidated or need recompiling.
Hope that's clear.
Edit:
Examples...
With package variables in dependency package...
SQL> create table a (x number);
Table created.
SQL> create package pkg_a is
  2    procedure mydependantproc;
  3  end;
  4  /
Package created.
SQL> create package body pkg_a is
  2    state_var number;
  3    procedure mydependantproc is
  4      local_var number;
  5    begin
  6      select x into local_var from a;
  7      state_var := local_var;
  8    end;
  9  end;
10  /
Package body created.
SQL> insert into a values (1);
1 row created.
SQL> exec pkg_a.mydependantproc;
PL/SQL procedure successfully completed.
SQL> alter table a add (y number);
Table altered.
SQL> exec pkg_a.mydependantproc;
BEGIN pkg_a.mydependantproc; END;
ERROR at line 1:
ORA-04068: existing state of packages has been discarded
ORA-04061: existing state of package body "CRISP_INTELL.PKG_A" has been invalidated
ORA-06508: PL/SQL: could not find program unit being called: "CRISP_INTELL.PKG_A"
ORA-06512: at line 1
SQL>And with the package variables dissassociated into another package spec...
SQL> create table a (x number);
Table created.
SQL> create package pkg_a is
  2    procedure mydependantproc;
  3  end;
  4  /
Package created.
SQL> create package pkg_b is
  2    state_var number;
  3  end;
  4  /
Package created.
SQL> create package body pkg_a is
  2    procedure mydependantproc is
  3      local_var number;
  4    begin
  5      select x into local_var from a;
  6      pkg_b.state_var := local_var;
  7    end;
  8  end;
  9  /
Package body created.
SQL> insert into a values (1);
1 row created.
SQL> exec pkg_a.mydependantproc;
PL/SQL procedure successfully completed.
SQL> alter table a add (y number);
Table altered.
SQL> exec pkg_a.mydependantproc;
PL/SQL procedure successfully completed.
SQL>;)
Message was edited by:
blushadow