-- get the process id from Linux (use top or ps)
-- the process id is spid in v$process
select sql_id from v$session where paddr in (select addr from v$process where spid in (4567))

-- put the sql_id from v$session into v$sqlarea/v$sql_text/v$sql
select sql_text from v$sqlarea where sql_id = 'ap3qms77rt67k'
-- this will display the sql that the process is executing

-- In one query
select sql_text
from v$sqlarea
where sql_id = 
(select sql_id from 
 v$session where paddr in 
 (select addr from v$process where spid = 1820)
);

			

To search for a string (grep) in files recursively with Powershell (example):

   gci -recurse -include *.sql|%{gc $_} | %{$_|select-string "dba"}

To get the filename(s):

   gci -recurse -include *.txt|%{$Filename=$_;gc $_} | %{$res=$_|select-string "dba";if ($res) {Write-Host "$Filename"}}

-- Get object_id from object name
select OBJECT_ID('[dbo].[testobject]')

-- get object_name from object id
select OBJECT_NAME(213575799)

Use this query in conjunction with sp_who to display running tasks and determine whether there are sessions blocking other sessions, and who is executing the query (sp_who)

SELECT command,
            r.session_id, r.blocking_session_id,
            s.text,
            start_time,
            percent_complete, 
            CAST(((DATEDIFF(s,start_time,GetDate()))/3600) as varchar) + ' hour(s), '
                  + CAST((DATEDIFF(s,start_time,GetDate())%3600)/60 as varchar) + 'min, '
                  + CAST((DATEDIFF(s,start_time,GetDate())%60) as varchar) + ' sec' as running_time,
            CAST((estimated_completion_time/3600000) as varchar) + ' hour(s), '
                  + CAST((estimated_completion_time %3600000)/60000 as varchar) + 'min, '
                  + CAST((estimated_completion_time %60000)/1000 as varchar) + ' sec' as est_time_to_go,
            dateadd(second,estimated_completion_time/1000, getdate()) as est_completion_time 
FROM sys.dm_exec_requests r
CROSS APPLY sys.dm_exec_sql_text(r.sql_handle) s
--WHERE r.command like ('%DBCC%')

See the article:

http://sqlmag.com/database-performance-tuning/seven-step-process-changing-database-collation

Real Memory Consumption = Total – (free + buffers + cached)

# free -m


             total       used       free     shared    buffers     cached
Mem:         15943      15678        265          6        511       3706
-/+ buffers/cache:      11460       4483
Swap:         8159          0       8159


# cat /proc/meminfo|grep -i huge

AnonHugePages:         0 kB
HugePages_Total:    4916
HugePages_Free:     3413
HugePages_Rsvd:       35
HugePages_Surp:        0
Hugepagesize:       2048 kB


The total memory reserved for huge pages is approximately 10 G ((4916 * 2048) /1024/1024)
This is approximately equal to 'used' on the second line of the 'free -m' command 11460/1024 = 11G

On an Oracle database server, the Huge Pages should be about 70-80% of the physical RAM  - varies with size, not a hard rule.

On an Oracle database server, the ulimits for the oracle user should be set accordingly - this means that the Oracle user
hard and soft limits for memory should be set high enough

Following files are modified to enable Huge Pages and disable transparent huge pages

/etc/grub.conf	
kernel …… transparent_hugepage=never
--> reboot

Example:
8G RAM --> set 70% for Huge Pages = 5.6G --> set vm.nr_hugepages=2688 in /etc/sysctl.conf --> 5.55G HugePages

--> 2 databases with SGA_TARGET set to 2.6G or 1 database with SGA_TARGET set to 5.5G

MEMORY_TARGET set to 0 (AMM should be disabled when Huge Pages are configured)

/etc/sysctl.conf	
vm.nr_hugepages=2688
(a number representing the number of pages – no unit)
Multiply by 2048 (K) and divide by 1024*1024 to get the number of GB of memory --> 5.55 G in this case

vm.hugetlb_shm_group=3000

/etc/security/limits.conf	
e.g set 7G = 7*1024*1024 = 7340032          --> for a server with 8G of memory

Another example for memlock ulimits:
Set the value (in KB) slightly smaller than installed RAM. e.g. If you have 64GB RAM installed, you may set 
soft memlock 60397977
hard memlock 60397977
(works out to 57G)