V$MYSTAT delta values

Here is a little script I use from time to time to look at V$MYSTAT values and displaying on one line a set of statistics with their delta value between two calls. The first script, _mystat_init.sql, initializes the variables. The second one displays the values, such as:

SQL> @ _mystat_diff.sql

db block changes        redo size undo change vector size     redo entries
---------------- ---------------- ----------------------- ----------------
          57,371       15,445,852               6,111,608           37,709

Those two scripts are generated by defining the statistics:

define names="'redo size','redo entries','undo change vector size','db block changes'"

abd running the following to spool the two scripts:

sqlplus -s / as sysdba <<'END'
set pagesize 0 feedback off linesize 1000 trimspool on verify off echo off
with stats as (
  select rownum n,stat_id,name from (select stat_id,name from v$statname where name in (&names) order by stat_id)
)
select 'define LAG'||stat_id||'=0' from stats
union all
select 'column "CUR'||stat_id||'" new_value '||'LAG'||stat_id||' noprint' from stats
union all
select 'column "DIF'||stat_id||'" heading '''||name||''' format 999G999G999G999' from stats
.
spool _mystat_init.sql
/
spool off
with stats as (
  select rownum n,stat_id,name from (select stat_id,name from v$statname where name in (&names) order by stat_id)
)
select 'set termout off verify off' from dual
union all
select 'select ' from dual
union all
select '   '||decode(n,1,' ',',')||'"CUR'||stat_id||'" - '||'&'||'LAG'||stat_id||' "DIF'||stat_id||'"' from stats
union all
select '   '||',nvl("CUR'||stat_id||'",0) "CUR'||stat_id||'"' from stats
union all
--select ','''||'&'||'1'' comments' from dual
--union all
select q'[from (select stat_id,value from v$mystat join v$statname using(statistic#) where name in (&names)) pivot (avg(value)for stat_id in (]' from dual
union all
select '   '||decode(n,1,' ',',')||stat_id||' as "CUR'||stat_id||'"' from stats
union all
select '))' from dual
union all
select '.' from dual
union all
select 'set termout on' from dual
union all
select '/' from dual
.
spool _mystat_diff.sql
/
spool off
END

Then, in sqlplus or SQLcl, you run:

SQL> _mystat_init.sql

to initialize the values to 0 and:

SQL> @ _mystat_diff.sql

each time you want to display the difference from last call.