It's kinda real-world problem and I believe the solution exists but couldn't find one.
So We, have a Database called Transactions that contains tables such as Positions, Securities, Bogies, Accounts, Commodities and so on being updated continuously every second whenever a new transaction happens. For the time being, We have replicated master database Transaction to a new database with name TRN on which we do all the querying and updating stuff.
We want a sort of monitoring system ( like htop process viewer in Linux) for Database that dynamically lists updated rows in tables of the database at any time.
TL;DR Is there any way to get a continuous updating list of rows in any table in the database?
Currently we are working on Sybase & Oracle DBMS on Linux (Ubuntu) platform but we would like to receive generic answers that concern most of the platform as well as DBMS's(including MySQL) and any tools, utilities or scripts that can do so that It can help us in future to easily migrate to other platforms and or DBMS as well.
To list updated rows, you conceptually need either of the two things:
The updating statement's effect on the table.
A previous version of the table to compare with.
How you get them and in what form is completely up to you.
The 1st option allows you to list updates with statement granularity while the 2nd is more suitable for time-based granularity.
Some options from the top of my head:
Write to a temporary table
Add a field with transaction id/timestamp
Make clones of the table regularly
AFAICS, Oracle doesn't have built-in facilities to get the affected rows, only their count.
Not a lot of details in the question so not sure how much of this will be of use ...
'Sybase' is mentioned but nothing is said about which Sybase RDBMS product (ASE? SQLAnywhere? IQ? Advantage?)
by 'replicated master database transaction' I'm assuming this means the primary database is being replicated (as opposed to the database called 'master' in a Sybase ASE instance)
no mention is made of what products/tools are being used to 'replicate' the transactions to the 'new database' named 'TRN'
So, assuming part of your environment includes Sybase(SAP) ASE ...
MDA tables can be used to capture counters of DML operations (eg, insert/update/delete) over a given time period
MDA tables can capture some SQL text, though the volume/quality could be in doubt if a) MDA is not configured properly and/or b) the DML operations are wrapped up in prepared statements, stored procs and triggers
auditing could be enabled to capture some commands but again, volume/quality could be in doubt based on how the DML commands are executed
also keep in mind that there's a performance hit for using MDA tables and/or auditing, with the level of performance degradation based on individual config settings and the volume of DML activity
Assuming you're using the Sybase(SAP) Replication Server product, those replicated transactions sent through repserver likely have all the info you need to know which tables/rows are being affected; so you have a couple options:
route a copy of the transactions to another database where you can capture the transactions in whatever format you need [you'll need to design the database and/or any customized repserver function strings]
consider using the Sybase(SAP) Real Time Data Streaming product (yeah, additional li$ence is required) which is specifically designed for scenarios like yours, ie, pull transactions off the repserver queues and format for use in downstream systems (eg, tibco/mqs, custom apps)
I'm not aware of any 'generic' products that work, out of the box, as per your (limited) requirements. You're likely looking at some different solutions and/or customized code to cover your particular situation.
Related
We're running Oracle 12c SE. I've read a lot of postings that say v$segment_statistics may have information on which are the most frequently queried or updated objects. However, can that be broken down? Say that one might want to see during what times of the day certain objects are hotter than other objects, or perhaps number of physical reads or writes per hour for a given table?
Does Oracle SE offer this an any of the v$ views?
It sounds like you are describing dba_hist_seg_stat which is one of the tables that is populated as part of the Automatic Workload Repository (AWR). If you're on the standard edition, I don't believe querying these views would violate your license agreement but I don't keep up to date with changes to licensing terms particularly for the standard edition.
You could replicate this functionality yourself by putting together a job that runs every few minutes, queries v$segment_statistics, and writes the delta from the prior snap to a custom table. You could then query that table to see what activity was going on at different points in time.
At work, my team accesses and works in a number of different databases using our team login. We have a ton of tables and views in each respective schema and I would guess that only ~10% are used regularly. As such, I would like to clean up these schemas to keep only those tables and views which are actually used and delete all the other ones (or at least archive them).
Is there any way for me to see the last time that a view was run, or the last time that a table was queried? My thinking is that if I can see that a view/table hasn't been used in x amount of time, then I'd feel more comfortable dropping it. My fear is that without such a process, I might drop tables/views that are used in Tableau dashboards and for other purposes.
Please check this Link
DBA_HIST tables can show you data depending till what date data is stored but not beyond that and it wont be conclusive.
We are facing one issue in our project i.e. Data verification issue.
The project is about Replication of data from Sybase to oracle DBs.
The table structures for Table A across Sybase, Oracle is same.
Same column and primary key combination across all the databases.
e.g. If Sybase has Table A with columns a, b and C
same table with same name and same columns will be available in different databses.
We are done with replication stuff part.But we faced some silent failure like data discrepancy just wondering if there will any tool already available for this.
Any information on his would be helpful. Thanks.
Sybase (now SAP) has a couple products that can be used for data comparisons and reconciliation:
rs_subcmp - an older, 32-bit tool that comes with the Sybase Replication Server product that can be used to compare data between
source and target; SQL reconciliation scripts can be generated from
the differences and then applied to the target to bring it in sync
with the source; if your tables are more than 1GB in size you can
still use rs_subcmp but you'll need to create multiple comparison
jobs (via where clauses) to work on different subsets of your tables
[I don't recall if rs_subcmp can be use for heterogeneous
replication setsup, eg, ASE-Oracle.]
Data Assurance (DA) - the newer, 64-bit product ... also from
Sybase ... which can also compare data and (re)sync the target(s)
from the source (either via SQL reconciliation scripts or directly);
DA is capable of handling comparisons between a handful of
different RDBMS products (eg, ASE-Oracle); I'm currently working on a
project where one of the requirements is to validate (and reconcile
where needed) 200+TB of data being migrated from Oracle to HANA and
I'm using DA for the validation/reconciliation portion of the project
As #TenG has hinted at with his answer, there's a good bit of effort involved to compare data and generate code to reconcile the differences. Rolling your own code is doable but will entail a lot of work. If you've got the money you'll likely find 3rd party tools can get most/all of the work done for you.
If you used a 3rd party product to replicate your data from Sybase to Oracle, you may want to see if the same vendor has a comparison/validation/reconciliation tool you could use.
I've worked on a few migration projects and a key part has always been data reconciliation.
I can only talk about the approaches we took, based on constraints around tools available and minimising downtime, and constraints of available space.
In all cases I took to writing scripts that worked on two levels - summary view and "deep dive". We couldn't find any tools readily available that did what we wanted in a timely enough manner. In fact even the migration tools we found had limitations (datapump, sqlloader, golden gate, etc) and hand coded scripts to handle the bits that we found to be lacking or too slow in the standard tools.
The summary view varied from project to project. It was part functional based (do the accounting figures for transactions match) for the users to verify, and part technical. For smaller tables we could just write simple reports and the diff was straight forward.
For larger tables we wrote technical reports that looked at bands of data (e.g group the PK into 1000s) collect all the column data and produce checksum, generating a report for each table like:
PK ID Range Start Checksum
----------------- -----------
100000 22773377829
200000 38938938282
.
.
Corresponding table pairs from each database were then were "diff"d against each other to highlight discrepancies. Any differences that were found could then be looked at in more detail.
The scripts were written in such a way to allow them to run in parallel looking at discrete bands. Te band ranges were tunable as well to get the best throughput. This obviously sped things up.
The scripts were shell scripts firing off sqlplus reports, and similar for the source database.
On one project there wasn't enough diskspace to do these reports, so I wrote a Java program that queried the two databases side by side, using block queues to fetch and compare rowsets. Being in memory meant this was super fast.
For the "deep dive" we looked at the details for key tables, or for tables that reports a checksum difference.
For the user reports, the users would specify what they wanted to see, and we wrote the reports accordingly.
On the last project, the only discrepancies found were caused by character set conversion issues (people names with accents weren't handled correctly).
On projects where the overall dataset was smaller we extracted the data to XML files and wrote a Java tool to processes pairs and report differences.
The SAP/Sybase rs_subcmp tool is pretty powerful and also pretty hard to use. For details see:
https://help.sap.com/viewer/075940003f1549159206fcc89d020515/16.0.3.3/en-US/feb58db1bd1c1014b134ef4efef25563.html?q=rs_subcmp
You have to pass it key field information, but once you do that, it can retry/restart the compare streams after transient differences. Pretty fancy.
rs_subcmp expects to work on Sybase data source. So to compare against Oracle, you'd probably have to setup one of those Sybase-to-Oracle gateway products ($$$$$).
Could you install the Oracle ODBC drivers and configure them to allow Sybase clients to access Oracle? I'm guessing not (but that's outside the range of my experience).
Note the "-h" option for rs_subcmp. The docs just say it runs a "fast comparison", but what it's actually doing is running queries using the hashbytes() function. Something like:
select keyfield1,keyfield2, hashbytes("Md5",datacol1,datacol2,datacol3)
from mytable
So this sort of query might be good for the "summary view" type comparison discussed above (if the Oracle STANDARD_HASH() function output matches up with the Sybase hashbytes() function (again, outside my experience))
Note, as of ASE 16, there was a bug with the hash() & hashbytes() functions running the Md5 hash option against large varbinary columns where they could use up all procedure cache, potentially crashing the server (CR 811073)
When two databases are attached is there a hit in performance compared to having a separate connection to each? Also, if I was writing data to one of the attached databases would both databases be locked or just the one being written to?
The reason I ask is it just seems simpler to me to have one connection that I ATTACH / DETACH each database to / from as it becomes needed / redundant rather than opening and closing connections to each of them all the time. My app doesn't have any threads.
Transaction are atomic over all attached databases; this requires creating a separate master journal in addition to all the normal rollback journals of the actual databases.
When having attached databases, table names (and PRAGMA statements) might require that the database name is added.
For these reason, ATTACH is usually used only when you actually need to access multiple databases in the same query.
I would like to implement a synchronization between a source SQL base database and a target TripleStore.
However for matter of simplicity let say simply 2 databases. I wonder what approaches to use to have every change in the source database replicated in the target database. More specifically, I would like that each time some row changes in the source database that this can be seen by a process that will read the changes and populate the target database accordingly while applying some transformation in the middle.
I have seen suggestion around the mechanism of notification that can
be available in the database, or building tables such that changes can
be tracked (meaning doing it manually) and have the process polling it
at different intervals, or the usage of Logs (change data capture,
etc...)
I'm seriously puzzle about all of this. I wonder if anyone could give some guidance and explanation about the different approaches with respect to my objective. Meaning: name of methods and where to look.
My organization mostly uses: Postgres and Oracle database.
I have to take relational data and transform them in RDF so as to store them in a triplestore and keep that triplestore constantly synchronized with the data is the SQL Store.
Please,
Many thanks
PS:
A clarification between ETL and replication techniques as in Change Data capture, with respect to my overall objective would be appreciated.
Again i need to make sense of the subject, know what are the methods, so i can further start digging for myself. So far i have understood that CDC is the new way to go.
Assuming you can't use replication and you need to use some kind of ETL process to actually extract, transform and load all changes to the destination database, you could use insert, update and delete triggers to fill a (manually created) audit table. Columns GeneratedId, TableName, RowId, Action (insert, update, delete) and a boolean value to determine if your ETL process has already processed this change. Use that table to get all the changed rows in your database and transport them to the destination database. Then delete the processed rows from the audit table so that it doesn't grow too big. How often you have to run the ETL process depends on the amount of changes occurring in the source database.