Oracle flashback data archive get last x records - oracle

We're using Oracle FDA for auditing, and I am trying to retrieve the last x records that a user had so I can compare them and see what change with each transaction. I've been googling around for quite some time now, and I can't quite figure out how to do that with an FDA query. I know how to retrieve a particular row as of a particular date and time, like:
select * from user
AS OF TIMESTAMP
TO_TIMESTAMP ('12302017:17:52:00','MMDDYYYY:HH24:MI:SS')
where guid = hextoraw('0A96318C1E0E45ADB5EAE1C94EA8F7B8');
But how would I be able to leverage this to get me a list of all the transaction that user has had so I can get, say, the last 10?

Related

Selecting all User Created Tables in ORACLE

I am using Oracle Xpress Edition. I want to know how to select only user created tables in Oracle DB.?
I am using this query:
select * from user_tables;
But it showing 24 rows. But i have only created 6 table.I don't know why & from where other tables (like APEX$_WS_FILES,DEPT, DEMO_USERS,APEX$_ACL,, APEX$_WS_HISTORY, etc) are showing.
How to avoid those useless table.?
These tables were presumably created during any Oracle APEX related installation. You can use the below steps to get rid of them.
SELECT * FROM ALL_OBJECTS WHERE OBJECT_TYPE = 'TABLE' AND OWNER = 'your_user' ORDER BY created;
As these tables have been installed via an application, they most
probably have been installed in a small and coherent time window. What
I mean here is that probably they have been installed within a time
frame of 30 mins, 1 hr or so. So if you order them by creation time,
they will all flock to consecutive rows in the output of above query.
Identify the time frame in which they have been started and
finished installing those tables. Write the above query once again to
filter that time frame out. You are then expected to get only your
tables.

design options to query from two different oracle databases

We have a transactional database with just 2 weeks of data and another archive database which holds data older than 2 weeks. Both DBs share the same schema structure and are in separate servers. We have a reporting application which queries data from both these databases where the user selects which database he wants to query by using a dropdown selection. In order to improve user experience we are thinking to do away with the dropdown selection by making the DB selection transparent in the background. Below are the few options we had in mind
Use UNION for the 2 select queries via DB links
Query DB1 first and if no records query DB2
Since the data volume is more we are apprehensive about our choices.
Appreciate if anyone has any other suggestions on how to approach this.
In my particular opinion, the best two choices are:
always give the user the data newer than a relative date (e.g. the last three months of data).
always give the user the last n data (e.g. the newest 250 rows).
Give all data will be inefficient when you have a big dataset.
But if you want to strengthen the autonomy and protect the user's work (two important design principles in user interfaces) then you must let the user configure the relative time or the number of data items desired. Or you can also let the user explore all/older data in particular situation (e.g. using a special window, a pagination system, a particular interface or a completly new use case).
Let's see two examples. (I assume that user is querying the server with newest data and OLD is the name of the dblink you use to reference the server with the data older than two weeks. I also assume that the target table is named DATATABLE and the column with the date is called DATADATE).
To retrieve the last three months (first choice):
SELECT * FROM DATATABLE
UNION ALL
SELECT * FROM DATATABLE#OLD WHERE MONTHS_BETWEEN(SYSDATE, DATADATE) >= 3;
And, to retrieve the last 250 rows (second choice):
SELECT *
FROM (SELECT * FROM DATATABLE ORDER BY DATADATE DESC)
WHERE ROWNUM <= 250;
UNION ALL
SELECT *
FROM (SELECT * FROM DATATABLE#OLD ORDER BY DATADATE DESC)
WHERE ROWNUM <= (250 - (SELECT COUNT(*) FROM DATATABLE));

oracle select and concurrent insert :: To check email availability

We have simple case, We have a table with column emailId i.e. unique.....using oracle DB
Question#1
Multiple concurrent user can check if some email id is available or not. Like 2 user that same time check availability of: abc#test.com
session1: select emailid from user_table;
//If not present allow user to complete rest of the process & insert info
session2: select emailid from user_table;
Now both session will get that this email id (abc#test.com) is available & both try to insert, I know one of them will get error upon insertion BUT how we can make sure only 1 user get availability & other get not available upon select ??
Question#2
Also in case both sessions inserted the same value, then first will succeed, is there ways that 2nd session update that row instead of throwing error. Like we have another column for timestamp & want that 2nd session instead of throwing error simple update the timestamp column ?
As this is a rather abstract question, here are only some general guidelines:
To deal with concurrent insert in a table, you need an unique index, and be prepared in your code to deal with ORA-00001 error unique constraint violated. Never rely only on check before insert(unless you have somehow exclusive access to your table -- and even if so ... as of myself, I would add an unique index: doesn't cost much and make me sleep better)
Oracle has a MERGE statement that allows you update or insert based on a condition. This operation is sometimes called an upsert. By using that keywork you should be able to find more informationsSee Oracle: how to UPSERT (update or insert into a table?) for example.
Now for, some thoughts about you specific case (maybe):
The only way for the system to work as you suggested, would be to make some kind of reservation when you check for availability (i.e.: immediately insert the row, instead of just select). And then update the row when the user confirm. But that means: (1) you will have to somehow deal with never-confirmed reservations (2) that doesn't dispense you to have an unique index, and to deal with ORA-00001.

Oracle: Monitoring changes in v_$parameter

Long time user, first time "asker".
I am attempt to construct an Oracle procedure and/or trigger that will compare two tables with the MINUS operation and then insert any resulting rows into another table. I understand how to do the query in standard SQL, but I am having trouble coming up with an efficient way to do this using PL/SQL.
Admittedly, I am very new to Oracle and pretty green with SQL in general. This may be a silly way to go about accomplishing my goal, so allow me to explain what I am attempting to do.
I need to create some sort of alert that will be triggered when the V_$PARAMETER view is changed. Apparently triggers can not respond to changes to view but, instead, can only replace actions on views...which I do not wish to do. So, what I did was create a table that to mirror that view to essentially save it as a "snapshot".
create table mirror_v_$parameter as select * from v_$parameter;
Then, I attempted to make a procedure that would minus these two so that, whenever a change is made to v_$parameter, it will return the difference between the snapshot, mirror_v_$parameter. I trying to create a cursor with the command:
select * from v_$parameter minus select * from mirror_v_$parameter;
to be used inside a procedure, so that it could be used to fetch any returned rows and insert them into another table called alerts_v_$parameter. The intent being that, when something is added to the "alert" table, a trigger can be used to somehow (haven't gotten this far yet) notify my team that there has been a change to the v_$parameter table, and that they can refer to alerts_v_$parameter to see what has been change. I would use some kind of script to run this procedure at a regular interval. And maybe, some day down the line when I understand all this better, manipulate what goes into the alerts_v_$parameter table so that it provides better information such as specifically what column was changed, what was its previous value, etc.
Any advice or pointers?
Thank you for taking the time to read this. Any thoughts will be very appreciated.
I would create a table based on the exact structure of v_$parameter with an additional timestamp column for "last_update", and periodically (via DBMS_Scheduler) merge into it any changes from the real v_$parameter table and capture the timestamp of any detected change.
You might also populate a history table at the same time, either using triggers on update of your table or with SQL.
PL/SQL is unlikely to be required, except as a procedural wrapper to the SQL code.
Examples of Merge are in the documentation here: http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_9016.htm#SQLRF01606

Oracle 10g - Determine the average of concurrent connections

Is it possible to determine the average of concurrent connections on a 10g large database installation?
Any ideas??
This is probably more of a ServerFault question.
On a basic level, you could do this by regularly querying v$session to count the number of current sessions, store that number somewhere, and average it over time.
But there are already good utilities available to help with this. Look into STATSPACK. Then look at the scripts shown here to get you started.
Alternatively you could install a commercial monitoring application like Spotlight on Oracle.
If you have Oracle Enterprise Manager set up you can create a User Defined Metric which records SELECT COUNT(*) FROM V$SESSION. Select Related Links -> User Defined Metrics to set up a new User Defined Metric. Once it collects some data you can get the data out in raw form or it will do some basic graphing for you. As a bonus you can also set up alerting if you want to be e-mailed when the metric reaches a certain value.
The tricky bit is recording the connections. Oracle doesn't do this by default, so if you haven't got anything in place then you won't have a historical record.
The easiest way to start recording connections is with Oracle's built in audit functionality. It's as simple as
audit session
/
We can see the records of each connection in a view called dba_audit_session.
Now what? The following query uses a Common Table Expression to generate a range of datetime values which span 8th July 2009 in five minute chunks. The output of the CTE is joined to the audit view for that date; A count is calulated for each connection which spans a five minute increment.
with t as
( select to_date('08-JUL-2009') + ((level-1) * (300/86400)) as five_mins
from dual connect by level <= 288)
select to_char(t.five_mins, 'HH24:MI') as five_mins
, sum(case when t.five_mins between timestamp and logoff_time
then 1
else 0 end) as connections
from t
, dba_audit_session ssn
where trunc(ssn.timestamp) = to_date('08-JUL-2009')
group by to_char(t.five_mins, 'HH24:MI')
order by t.five_mins
/
You can then use this query as the input into a query which calculates the average number of connections.
This is a fairly crude implementation: I choose five minute increments out of display considerations , but obviously the finer grained the increment the more accurate the measure. Be warned: if you make the increments too fined grained and you have a lot of connections the resultant cross join will take a long time to run!

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