ORA-06553: PLS-907 Solution

Error
ORA-06553: PLS-907: cannot load library unit aaa (object) 
(referenced by bbb)

Solution
Compile related object (bbb)
SQL> ALTER FUNCTION HR.BBB COMPILE;

ORA-00059 solution

Error
ORA-00059: maximum number of DB_FILES exceeded

Solution
Check limit that total number of db files
SQL> show parameter db_files;
-- e.g. 250

Edit parameter file:
# add this on bottom
*.db_files=500

Shutdown and startup database:
SQL> shu immediate;
SQL> startup;

Extra:
If database is using spfile:
SQL> show parameter spfile;
-- output should be not empty

Delete spfile under $ORACLE_HOME/dbs directory such as 
"spfileALPERDB.ora"

At last, shutdown and startup database again.

How to restore database object such as package body via flashback?

Note that below SQL gets output if it is still in UNDO tablespace.
SQL> 
SELECT text  FROM all_source
       AS OF TIMESTAMP TO_TIMESTAMP ('21-04-2017 14:30:00', 'DD-MM-YYYY HH24:MI:SS')
 WHERE name = 'PRG_BODY_ALPER' 
AND TYPE = 'PACKAGE BODY';

for DBA: dba_source table

Related: https://ozsoyler.blogspot.com/2016/12/how-to-rollback-committed-data-from.html

How to see TOP 10 SQL that consuming system resources highly?

e.g.
select * from
(
select * from v$sql
order by DISK_READS desc
)
where rownum < 11

options for order by:
RUNTIME_MEM, EXECUTIONS, DISK_READS, SORTS, ELAPSED_TIME

for old querries:
select * from dba_hist_sqltext where sql_id = '8j2hv3c6wskdy'

for SQL plan:
select * from V$SQL_PLAN where sql_id = '8j2hv3c6wskdy'

find the object location of SQL
select * from all_source where owner <> 'SYS' and upper(text) like '%ABC%'

How to find and investigate a process in top command output?

Total connection by machine:
SQL> select machine, count(*) from v$session group by machine order by 2;

Total number of database user who connected:
SQL> select count(1) "NO. Of DB Users Connected", to_char(sysdate,'DD-MON-YYYY:HH24:MI:SS') sys_time from v$session where username is NOT NULL;

Define a process(pid) from top:
17831 ora11g .. ora_m000_ALPERDB  

Get detailed info from database:
SQL> select * from v$process where spid = 17831;
-> M000 means MMON Slave Process
-> e.g. pid -> 16, sid -> 555

SQL>
SELECT s.username, osuser, process machine, p.terminal, type, sid, s.serial#, s.program
FROM v$session s, v$process p
WHERE p.pid = 16
AND s.paddr = p.addr;

SQL> select * from gv$session where sid = 555;

Get sql from below code related to example process if it has SQL:
SQL>
SELECT 
      s.sid
     ,s.CLIENT_INFO
     ,s.MACHINE
     ,s.PROGRAM
     ,s.TYPE
     ,s.logon_time
     ,s.osuser
     ,sq.sorts
     ,sq.DISK_READS
     ,sq.BUFFER_GETS
     ,sq.ROWS_PROCESSED
     ,sq.SQLTYPE
     ,sq.SQL_TEXT
 FROM gv$session s    
    , gv$sql sq
WHERE s.SQL_HASH_VALUE = sq.HASH_VALUE
  --AND s.inst_id= 1
  AND s.sid = 555 
  AND sq.inst_id= s.inst_id

How to get value from xml node?

e.g. xml file:
<A>
<B value="Alper XML">
<C value="Alper XML 2">
</C>
</B>
</A>

catch the value:
@echo off
for /F tokens^=1^,2^delims^=^"^= %%a in (example.xml) do (
if "%%a" equ "<B value" (
rem %%a first column, %%b second column
echo example value: %%b
)
)
)
pause

output:
example value: Alper XML