I am creating an oracle view basically as a read-only summary of data from other tables. It is not necessary to update the view every time if there is any updates to associated tables otherwise the workload will be huge and a waste. It is better to refresh the view every 5 minutes and then the front end can receive the latest data that will be all.
However, how to setup the oracle view refreshing interval? Do we have to settle this constraints in PL/SQL?
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We are using Oracle Materialized view to extract data for a reporting system. The setting of the MV is to refresh on every commit.
After migrating to Oracle 19 form Oracle 12 system was very slow for few days and eventually became unresponsive after few days due to various bugs in Oracle 19 related to Materialized View.
We did a workaround of changing MV setting from on commit to OnDemand every 5 min to solve this issue.
The parent table on which this view is created gets updated every second and has 2 million records.
Having a MV on a table which is updated so frequently is fundamentally not a good design.
We don't want to depend on Oracle patches to fix this and planning to redesign this table.
Can I change this view to simple view and possibly apply all possible ways to improve query response time and expect that I will have view query returned in few seconds given I have 2 mil records in Parent table.
Assume that table has basic datatypes only and view is reading about 5-6 fields.
We tried oncommit to ondemand as a workaround but as per the business need, we need committed data for the reporting system and cannot be delayed more than one min.
In our oracle query, I used materialized view to improve the performance and saw a drastic change in performance time of query, response time is in .17 seconds now rather 30 seconds so its working in case we are working on historical data set and need to have one time refresh of materialized view but now requirement is if base table of materialized view would be updating frequently in that case it would be working as the refresh activity of materialized view would be consuming time as well, currently the base table has around 170000 records but in future definitely going to increase so is there any solution or option to resolve this. As i have tried to apply Indexes as well on the table but not able to achieve response time within .17 sec or around the last response time based on index creation was 18 sec.
I have an Oracle materialized view refreshed on demand. Since the view is pretty large, it takes a while to update. I am wondering: when do the updates really become visible to the queries that try read the view? Does RDBMS update the view in a buffer and then makes it visible when update is complete? Or will the changes gradually become visible to the reader? Is this possible to control this?
Materialized views can be refreshed on commit or on demand.
Oracle's documentation is quite good
https://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_6002.htm#i2116410
To have materialized views refresh incrementally you must use the FAST option and you must have materialized view logs to capture changes on the source tables.
If you schedule the demanded refreshes frequently there will be less work to be done for each refresh. If you schedule them less frequently there will be more work to be done. You need to investigate how changes on the source tables are distributed over time to choose well.
Changes will be visible to users when the refresh (whatever size) commits.
How to find out if changes made at known time in underlying table are already available in fast refreshing materialized view?
So far:
all_mview_analysis.LAST_REFRESH_DATE - this seems to be the start time of the refresh not end time? Is this value written when refresh is started or when it is finished?
all_mview_analysis.INCREFRESHTIM - docs say this is "Approximate refresh time, in seconds, for fast refresh". Approximate is not enough.
In other words: I have changed data at time x. I need to query if those changes made at time x are already included in materialized view or not. I want to wait as much as needed but as little as possible.
Database: Oracle 11g.
We have to create a materialised view in our database from a remote database which is currently in production. The view has about 5 crore records and is taking a long time. In between , the connection has snapped once and not even a single record persisted in our database. Since the remote database is production server, we get a very limited window to create the view.
My question is, can we have something like auto commit /auto start from where left at last time while the view is created so that we don't have to do the entire operation in one go ?
We are tying to make the query such that records can be fetched in smaller numbers as a alternate. But the data is read only for us and doesn't really have a where clause at this point which we can use.
Due to sensitive nature of data, I cannot post the view structure or the query.
No, you can not commit during the process of creating the view. But why don't you import the data to a table instead of a view? This would provide the possibility to commit in between. Furthermore this might provide the possibility, to load only the delta of changes maybe on daily basis - this would reduce the required time dramatically.