Trying to understand if there is any such concept like this in Oracle Database.
Let's say I have two Databases, Database_A & Database_B
Database_A has schema_A, is there a way I can attach this schema to Database_B?
What I mean by this is if there is a job populating a TABLE_A in schema_A, I can see that read-only view in Database_B. We are trying to split a big Oracle database into two smaller databases and have a vast PL/SQL code, and trying to minimize the refactoring here.
Sharding might be what you're looking for. The schemas and tables will still logically exist on all databases, but you can arrange the data to be physically stored in specific databases. There might be a way to setup shardspaces, tablespaces, and user default tablespaces in a way where each schema's data is automatically stored in a specific database.
But I haven't actually used sharding. From what I've read, it seems to be designed for massive distributed OLTP systems, and it is likely complicated to administer. I'd guess this feature isn't worth the hassle unless you have petabytes of data.
Related
We have transaction tables in Oracle and for reporting purposes we need this data transfered in real time to another flat Oracle table in another database. The performance of the report is great with table placed in this flat table.
Currently we are using golden gate for replication to the other database and using materialized view for this but due to some problems we need to switch to some other way of populating/maintaining this flat table. What options do we have?
It is a pretty basic requirement but the solutions I can see are for batch processing. Also if there are any other solutions you feel would better serve this purpose. Changing the target database to something other is also an option as there might be more such reports coming ahead.
I've tried to figure out which performance impacts the use of temporary tables has on an Oracle database. We want to use these tables in our ETL process to save temporary results. At this time we are using physical tables for this purpose and truncating this tables at the beginning of the ETL process. I know that the truncate process is very expensive and therefore I thought if it would be better to use temporary tables instead.
Have anyone of you experiences if there is a performance boost by using temporary tables in this scenario?
There were only some answers on this question regarding to the SQL Server like in this question. But I don't know if these recommendations also fit for the Oracle db.
It would be nice if anyone could list the advantages and disadvanteges of this feature and also point out in which scenarios this feature could be applicable.
Thanks in advance.
First of all: truncate is not expensive, a delete with no condition is very expensive.
Second: do your temporary table have indexes? What about external keys?
That could affect performance.
The temporary table works more or less like Sql Server (of course the syntax is different, like global temporary table), and both are just table.
You won't get any performance gain with temporary tables against normal table, they are just the same: they have a definition on DB, can have indexes, and are logged.
The only difference is that temporary table are exclusive to your session (except for global table) and that means if multiple scripts from multiple sessions refer to the same table, every one is reading/writing a different table and they cannot locking each other (in this case you could gain performance, but I think it's rarely the case).
We are planning a new system for a client in ORACLE 11g. I've been mostly in the Sql Server world for several years, and am not really current on the latest ORACLE updates.
One particular feature I'm wondering if ORACLE has added in by this point is some sort of logical "container" for database objects, akin to Sql Server's SCHEMA.
Trying to use ORACLE's schemas like Sql Server winds up being a disaster for code comparisons when trying to push from dev > test > live.
Packages are sort of similar, except that you can't put tables into a package (so they really only work for logical code grouping).
The only other option I am aware of is the archaic practice of having to prefix object names with a "schema" prefix, i.e. RPT_REPORTS, RPT_PARAMETERS, RPT_LOGS, RPT_USERS, RPT_RUN_REPORT(), with the prefix RPT_ denoting that these are all the objects dealing with our reporting engine say. Writing a system like this feels like we never left the 8.3 file-naming age.
Is there by this point in time any cleaner, more direct way of logically grouping related objects together in ORACLE?
Oracle's logical container for database objects IS the schema. I don't know how much "cleaner" and "more direct" you can get! You are going to have to do a paradigm shift here. Don't try to think in SQL Server terms, and force a solution that looks like SQL Server on Oracle. Get familiar with what Oracle does and approach your problems from that perspective. There should be no problem pushing from dev to test to production in Oracle if you know what you're doing.
It seems you have a bit of a chip on your shoulder about Oracle when you use terms like "archaic practice". I would suggest you make friends with Oracle's very rich and powerful feature set by doing some reading, since you're apparently already committed to Oracle for this project. In particular, pick up a copy of "Effective Oracle By Design" by Tom Kyte. Once you've read that, have a look at "Expert Oracle Database Architecture" by the same author for a more in-depth look at how Oracle works. You owe it to your customer to know how to use the tool you've been handed. Who knows? You might even start to like it. Think of it as another tool in your toolchest. You're not married to SQL Server and you're not being unfaithful by using Oracle ;-)
EDIT:
In response to questions by OP:
I'm not sure why that is a logistical problem. They can be thought of as separate databases, but physically they are not. And no, you do not need a separate data file for each schema. A single datafile is often used for all schemas.
If you want a "nice, self-contained database" ala SQL Server, just create one schema to store all your objects. End of problem. You can create other users/schemas, just don't give them the ability to create objects.
There are tools to compare objects and data, as in the PL/SQL Developer compare. Typically in Oracle you want to compare schemas, not entire databases. I'm not sure why it is you want to have multiple schemas each with their own objects anyway. What does is buy you to do that? Keep your objects (tables, triggers, code, views, etc.) in one schema.
At work we are thinking to move from Oracle to a NoSQL database, so I have to make some test on Cassandra and MongoDB. I have to move a lot of tables to the NoSQL database the idea is to have the data synchronized between this two platforms.
So I create a simple procedure that make selects into the Oracle DB and insert into mongo. Some of my colleagues point that maybe there is an easier(and more professional) way to do it.
Anybody had this problem before? how do you solve it?
If your goal is to copy your existing structure from Oracle to a NoSQL database then you should probably reconsider your move in the first place. By doing that you are losing any of the benefits one sees from going to a non-relational data store.
A good first step would be to take a long look at your existing structure and determine how it can be modified to affect positive impact on your application. Additionally, consider a hybrid system at the same time. Cassandra is great for a lot of things, but if you need a relational system and already are using a lot of Oracle functionality, it likely makes sense for most of your database to stay in Oracle, while moving the pieces that require frequent writes and would benefit from a different structure to Mongo or Cassandra.
Once you've made the decisions about your structure, I would suggest writing scripts/programs/add a module to your existing app, to write the data in the new format to the new data store. That will give you the most fine-grained control over every step in the process, which in a large system-wide architectural change, I would want to have.
You can also consider using components of Hadoop ecosystem to perform this kind of (ETL) task .For that you need to model your Cassandra DB as per the requirements.
Steps could be to migrate your oracle table data to HDFS (using SQOOP preferably) and then writing Map-Reduce job to transform this data and insert into Cassandra Data Model .
In an organization that has two applications each with its own Oracle database instance, what are the disadvantages of consolidating the two databases into one database with two schemas?
Backups and replicating the database are bigger and slower, probably. What else?
Some background:
The two databases are the "gold source" for their respective data. Each is critical to the operation of the organization and each is actually used by several appliations, tools, and reports (but each database is principally "owned" by one application). The need to join data across the databases, to relate entities in one to entities in the other, comes up frequently. For this reason there are DB links connecting the two and some cross-database materialized views to help with performance. There is an effort underway to reduce data duplication and these materialized views are under discussion. Some in the organization want to phase out DB links and materialized views and introduce more web services to make the data available across applications. My concern is that there are too many situations that require complex joins of data across the two databases so services that expose the data won't perform. Another approach for reducing DB links and materialized views is to consolidate the schemas into one database, but I want to make sure I'm not forgetting any critical disadvantages to that approach.
In a single consolidated database, you will lose some flexibility from a DBA point of view:
A database obviously can have only one version (10.2.0.5 for example), which means that upgrades and patches will affect all schemas -- this may be a bad thing in case of multiple vendor app requirement mismatch.
Similarly, some administrative tasks (restore database A to point in time t) may be more complicated with a single database.
Overall, you will have less administration tasks (a single backup, single patching...) but each task will be more critical since they will have a global effect.
On the development side, beware of namespace collisions: some features are global over a single database, for example:
directories,
public synonyms,
DB link
Schemas
This means that you will have some work to do if you want to consolidate two databases that have public synonyms with the same name that points to two different things.
Could have something to do with licence costs - scaling up vs. scaling out.
The biggest concern I would have is that all your code will need to be rewritten to account for the new database and schemas. Or at least looked at. This courl introduce new bugs. I don't know how Oracle handles refernces to different databases, so I'll use an example of what I mean using SQL Server syntax. If I was joining to two tables onthe same server in different databases my select would be something like this:
SELECT a.field1, b.field2
FROM database1.dbo.table1 a
JOIN database2.dbo.table2 b
ON a.myid = b.myFK
To go your your new consolidated idea, you would want to write:
SELECT a.field1, b.field2
FROM schema1.table1 a
JOIN schema2.table2 b
ON a.myid = b.myFK
You will need to be especially careful of any tables that have the same name in both databases now, this could cause some sneaky bugs.
Note these are not difficult changes but all SQL hitting your database would have to be examined to see if it will work or adjusted if not.
I'm not sure if just putting them in the same database would do it either. You might need to consolidate some tables to avoid the duplication across applications. (In this case add fields to reference the old id numbers for things people are used to looking up by id like person_id that may appear on old paperwork, so they can be researched) This is a fairly major rewrite with all the attendant possibilites to make things worse due to new bugs.
If you go down this path, I highly recommend that you read a book on refactoring datbases before you decide how to design.
its hard to tell by just the information provided, big in db world would be 100gb or more, so 2 dbs would be 200GB. if both db are not bigger than 100GB then size should not be a huge factor in the decision, replication and sync can be done on changes only and backups should not be a big difference (again this depends on specifics such as when backups are done or if downtime is possible or backups are done during non-peak times)
Other than that other factors are:
naming collisions in dbo's such as keys, foreign key names, table names, etc. some renaming of tables, store procedures names too.