Suppose the following scenario:
I have a master database that contains lots of data, in this database I have a key table that I'm going to call DataOwners for this example, the DataOwners table has 4 records, each record of each of the other tables in the database "belongs" directly or indirectly to a record of the DataOwners, and by belongs I mean is linked to it with foreign keys.
I also have other 2 slave databases with the exact same structure from my master database whose are only updated through replication from my master database, but SlaveDatabase1 should only have records from DataOwner 2 and SlaveDatabase2 should only have records from DataOwners 1 and 3 whereas MasterDatabase has records of DataOwners 1, 2, 3 and 4.
Is there any tool for Oracle that allows me to do this kind of selective record replication?
If not, is there any way to improve my replication method? which is:
add to each table a trigger that inserts the record changes in a group of replication tables
execute the commands of the replication tables at selected slaves
The simplest option would be to define materialized views in the various slave databases that replicate just the data that you want. So, for example, if there is a table A in the master database, then in slave database 1, you'd create a materialized view
CREATE MATERIALIZED VIEW a
<<refresh criteria>>
AS
SELECT a.*
FROM a#to_master a,
dataOwners#to_master dm
WHERE a.dataOwnerID = dm.dataOwnerID
AND dm.some_column = <<some criteria that selects DataOwner2>>
while slave database 2 has a very similar materialized view
CREATE MATERIALIZED VIEW a
<<refresh criteria>>
AS
SELECT a.*
FROM a#to_master a,
dataOwners#to_master dm
WHERE a.dataOwnerID = dm.dataOwnerID
AND dm.some_column = <<some criteria that selects DataOwner1 & 3>>
Of course, if the dataOwnerID can be hard-coded, you could simplify things and avoid doing the join. I'm guessing, though, that there is some column in the DataOwners table that identifies which slave a particular owner should be replicated to.
Assuming that you want only incremental changes to be replicated, you'd need to create some materialized view logs on the base tables in the master database. And you would probably want to configure refresh groups on the slave databases so that all the materialized views would refresh at the same time and would be transactionally consistent with each other.
Oracle Golden Gate software can do all these tasks. Insert/Update/Delete have the same order of the master db, so it can avoid the foreign keys and other constraint issues.
MasterDatabase Extract generates a trail file, then split out the data to DB 1,2,3 and 4.
It also can do multiple ways replications, i.e. DB 1 sends data back to the Master DB.
Besides the Golden Gate, trigger may be your other option. But it requires some programming.
Related
I want to ask you if there is a solution to auto-synchronize a table ,e.g., every one minute based on view created in oracle.
This view is using data from another table. I've created a trigger but I noticed a big slowness in database whenever a user update a column or insert a row.
Furthermore, I've tested to create a job schedule on the specified table (Which I wanted to be synchronized with the view), however we don't have the privilege to do this.
Is there any other way to keep data updated between the table and the view ?
PS : I'm using toad for oracle V 12.9.0.71
A materialized view in Oracle is a database object that contains the results of a query. They are local copies of data located remotely, or are used to create summary tables based on aggregations of a table's data. Materialized views, which store data based on remote tables, are also known as snapshots.
Example:
SQL> CREATE MATERIALIZED VIEW mv_emp_pk
REFRESH FAST START WITH SYSDATE
NEXT SYSDATE + 1/48
WITH PRIMARY KEY
AS SELECT * FROM emp#remote_db;
You can use cronjob or dbms_jobs to schedule a snapshot.
I have the following scenario and need to solve it in ORACLE:
Table A is on a DB-server
Table B is on a different server
Table A will be populated with data.
Whenever something is inserted to Table A, i want to copy it to Table B.
Table B nearly has similar columns, but sometimes I just want to get
the content from 2 columns from tableA and concatenate it and save it to
Table B.
I am not very familiar with ORACLE, but after researching on GOOGLE
some say that you can do it with TRIGGERS or VIEWS, how would you do it?
So in general, there is a table which will be populated and its content
should be copien to a different table.
This is the solution I came up so far
create public database link
other_db
connect to
user
identified by
pw
using 'tns-entry';
CREATE TRIGGER modify_remote_my_table
AFTER INSERT ON my_table
BEGIN INSERT INTO ....?
END;
/
How can I select the latest row that was inserted?
If the databases of these two tables are in two different servers, then you will need a database link (db-link) to be created in Table A schema so that it can access(read/write) the Table B data using db-link.
Step 1: Create a database link in Table A server db pointing to Table B server DB
Step 2: Create a trigger for Table A, which helps in inserting data to the table B using database link. You can customize ( concatenate the values) inside the trigger before inserting it into table B.
This link should help you
http://searchoracle.techtarget.com/tip/How-to-create-a-database-link-in-Oracle
Yes you can do this with triggers. But there may be a few disadvantages.
What if database B is not available? -> Exception handling in you trigger.
What if database B was not available for 2h? You inserted data into database A which is now missing in database B. -> Do crazy things with temporarily inserting it into a cache table in database A.
Performance. Well, the performance for inserting a lot of data will be ugly. Each time you insert data, Oracle will start the PL/SQL engine to insert the data into the remote database.
Maybe you could think about using MViews (Materialized Views) to replicate the data via database link. Later you can build your queries so that they access tables from database B and add the required data from database A by joining the MViews.
You can also use fast refresh to replicate the data (almost) realtime.
From perspective of an Oracle Database Admin this would make a lot more sense than the trigger approach.
try this code
database links are considered rather insecure and oracle own options are having licences associated these days, some of the other options are deprecated as well.
https://gist.github.com/anonymous/e3051239ba401e416565cdd912e0de8c
uses ora_rowscn to sync tables across two different oracle databases.
I am new to HDFS/HIVE. Need some advice. I have a background of RDBMS Data modelling.
I have a requirement of a daily report. The report requires fetching of data from two staging Tables(HIVE).
What if I create a table in HIVE, write a view to fetch records from staging to populate HIVE table. create a HIVE view pointing to HIVE table with where clause of selecting one-day data?
HIVE staging tables ---> 2. View to populate HIVE table --> 3. HIVE table ----> 4. View to fetch data from HIVE table created in 3.
what if I create a view on top of two staging HIVE tables (joining two tables with where clause to fetch one-day data)?
HIVE staging tables ---> 2. View to fetch data from HIVE staging tables
I want to know HIVE best practice and solution strategies.
View or not View but you need ETL process to load tables. ETL process can join, aggregate, etc, so you will be able use finally joined and aggregated data in the form star/snowflake or report table. Why do you need Views here? To reuse some common queries, to reduce complexity of some long complex queries, make interfaces to data, create logical entities, etc. You do not necessarily need View simply to join tables and load data to another table. All depends on your requirements. If reports should query data fast then data should be precalculated by ETL process. View is just wrapper over query, it will be calculated each time you query data.
I think its best if you have zero views, 1 single table, and make your partition the date field (but you can't partition on the date, so you have to store it as a string) ... this make it easier for the end user to have only 1 table... fewer tables.
This gives your users the ability to engage only the latest date they want, or leverage the full table.
I have two tables table1 in local system and table2 on another system. I created database link to table2 in local sytem I.e table2#anothersystem
I have two columns in both tables ID (number) & NAME (varchar). I want to execute any query on table1 such that after it's execution in table1 it will also be identically executed in table2.
In short I want to keep table1=table2. can anybody suggest trigger for it in Oracle 11g
As #justin-cave already mentioned, using triggers is definitely not the way to go. I'd opt for a materialized view (the cheap option). Check Oracle materialized view question for a starting point. When you have the appropriate license you could create a logical or physical standby database, or other Oracle-provided data replication options.
I have a question: I have a table (say tableA) in a database (say dbA) and I need to mirror tableA as another table (say tableB) in another database (say dbB).
I know this can be done via (materialised) view or via informatica. But by problem is that I need to sync DDL as well. For example if a column is added in tableA, the column should automatically reflect in tableB.
Can this be done anyway directly via oracle or Informatica.
(or I will have to write a procedure to sync table on basis of all_tab_cols).
Yes, you could:
create another database as a logical standby database with Data Guard
use Oracle Streams
I would use (2) if you just need a single table in the other database or (1) if you need an entire schema (or more).