Unix - whoami and who am i

In many unix books most of us have read these words or commands whoami and who am i..These commands are useful when you work in an environment where people have different login ids and you are using sudo access or are first logging thorugh a different name and then switching to another user.
suppose i login with username joe and then i use su - to switch to user pam. Now if i will use the command
$id
joe gid() uid()
$su - pam
password: *******
$
$id
pam gid() uid()
ok...now i will use whoami
$whoami
pam

ok and now i use who am i

$who am i
joe

So you see the difference. its very clear from the example.
Sometimes you might see many screens open, but you really don't know who had initially logged into the system . At that time these commands are very handy.

Track long running queries in Oracle

It happens sometime or shall i say most of the time that your manager or user calls and asks the DBA ...the db is very slow..can you check what is running in the system or can you check for any long running queries in the database. In this case oracle has provided us a view call v$session_longops, this is a fantastic view and it really helps in checking out for long running queries. for a simple example just run the query -

select * from v$session_longops where sofar <> totalwork;

if it is RAC you should use gv$session_longops.

This is just a basic example and will give you lots of information about long queries running in the system, and will also tell you how much work is done and how much work is left..time shall i say..

Oracle Database- Who is using my undo Tablespace??

It Happened once that i came in morning and logged onto the database. I was just checking tablespaces when i observed undo tablespace is totally full....so what was eatin up my undo..in such case oracle provides you a view called V$transaction that gives you information about transactions using Oracle db undo tablespace. This view can be joined with V$session and with help of this you can easily come to know which user is using your undo tablespace. In my case some developer has left running an update query which was to update a major table at night and had not committed..I called up the developer..and told him to either commit or rollback..he committed his transaction..and undo got freed..

Tracing a User Seeion in Oracle - DBMS_SUPPORT

Many a times we need to trace a user session.

For this oracle has supplied a package called DBMS_TRACE.

To Trace a user session we can start Sql Tracing by using -

exec dbms_support.start_trace_in_session(sid,serial#,binds=>true,waits=>true);

Since we are setting waits=> true this will capture wait information of Sqls.

And Binds=> true will capture bind values.

To stop tracing -

exec dbms_support.stop_trace_in_session(sid,serial#)

Oracle RAC with Veritas (SFRAC)

In one of the projects that we are handling, we have SFRAC. This is the first time i am workin on any setup that has Veritas Storage foundation for RAC implemented. I was much excited to work on something new , and after reading for sometime and going through veritas docs, i am somewhat comfortable in handling issues.
Will update this post more, in some time.

CRS Commands

CRS is cluster ready services. CRS controls oracle clusterware and services controlled by oracle cluster. For this there are CRS deamons that run continuously on both the nodes and monitor the operation of cluster.
In this post i will tell few basic commands to stop and start CRS.

To check whether crs deamons are running or not we use-

crsctl check crs

And if you have to check all services controlled by cluster, then use the command -

crs_stat -t

This will give you status of all services , In ideal conditions status is ONLINE and if service is down it will post the status as OFFLINE

Suppose i want to stop crs , in this case i will use -

crsctl stop crs

sometimes a service may get down due to some error , this can be started by using -

crs_start servicename