Those two tables are identical, the only difference is name, and one was created with the sequential SQL index on the ID column 1, 2, 3, etc. Both have a clustered index on the same column. Furthermore, if we right-click on it, hit Properties and select Fragmentation , since this is a brand new index, we should see both Page fullness the average percent full of pages and Total fragmentation logical fragmentation percentage taking into account multiple files values to be 0.
Since both tables are empty, we cannot really use them unless we have some data in them. We can do this by executing the code from below:. The above code inserts a thousand records into both tables. Both batches did the exact same thing. The only difference here is that we have our ID sequential on one table and non-sequential on the other. Just locate it in Object Explorer, right-click on it and hit Properties. If we now check the fragmentation, notice that the fragmentation is at 5. What do you think will happen if we insert another thousands record into this table?
Will it get worse or better? Head over to the index properties again, and notice the total fragmentation went down to 2. Sure thing. It gets better because with the sequential SQL Indexes it just keeps filling out the pages.
When it needs another page, it will just create it, fill it in, and so on without reorganizing or moving anything. Now, if we head over to non-sequential and check the fragmentation we can see a significantly higher value of I guarantee if we run the Insert statement one more time this number will go up even more:.
Hopefully, this example gives you an idea of how something as simple as putting an index in a field that is not sequential is essential to an SQL index. The question here is what do we do when performance starts to drop down or we get complains from other people that there is some performance degradation.
The first one is sys. If we quickly analyze the code, we can see that we are passing the database ID and we take the DMV and then join the sys. The query returned 96 indexes and on the top of the list is our test non-sequential SQL index but we also got some pretty high numbers below. Those are also havy fragmented indexes and they should be rebuild.
The second DMV is sys. As before, use the code from below and run it against a targeted database. I got nothing on my sample database, so I ran it against another one with actual traffic:. What this query will essentially do, is help us analyze unused SQL indexes same as before, just a minor change in Where clause to only grab user tables.
Furthermore, this will find seeks, scans, lookups, and updates of an index:. The major part here is seeks and scans. The rule of thumb is that the scans are bad, seeks are good. To give some idea of size, the primary database currently contains 3 big tables each with around million rows and takes up about GB storage space.
Over 5 million rows are added each day. Because of a critical disk space shortage predecessor did not archive old data or manage it's size at all , I was forced to delete about million rows from the largest table.
This process took over 25 hours to complete and the database needed to be cut off from customer-facing applications during that time. Now, I need to reindex the table because selects and inserts take a very long time. However, I can't just take the database offline indefinitely, I need to be able to estimate the amount of time needed to perform the reindex. I have never reindexed a table so large before, so I don't really have any good reference points to draw upon.
The primary table includes a clustered, monotonically-increasing primary key, and a non-unique non-clustered key as well. I have plenty of disk space available to perform the reindex. So my question is this: About how long do people thing this will take me?
What is a good rule of thumb for estimating reindexing time? No way to estimate how long it will take - so many different things would have an impact. The best answer would be how long has it taken in the past? If you can't determine that, next best option would probably be to try it on a similar non-production environment, but even that won't necessarily match i.
I can't add a second hyperlink, but google "online index operations sql server" and click the top link. Try running the following query against the database the query runs on SQL or above. Note this query will impact your server and should be run at a quiet time:. Since you say you cut out a very large amount of rows already, it shouldn't be a problem to run it during off-peak hours.
You could set up replication and offer that database to your customers while you clean up the old one and set it in read-only so they can still get any data they might need. You set the thresholds of when you want to defrag vs rebuild. It automatically detects which indexes it can rebuild online, and does that as well, giving you some uptime benefits. Index Rebuild Entire Index 2. Index Rebuild Index Volume 3. Index Update 4.
Index Repair. Index Rebuild Entire Index To perform an entire index rebuild, simply go in to the Vault Admin Console, find the Archive whose index you wish to rebuild, right click and go to properties, then go to the Advanced Tab and select the Rebuild Index button. What this will do is delete all the index volumes within the SQL Tables for that user as well as the physical directories themselves from the Index locations on your physical storage. The only one it will not delete is the First index volume, it will simply delete the contents From there, it will then start re-indexing items from the first Index Sequence number in the database all the way through to the highest index sequence number in the database.
This will cause EV to open each and every piece of archived email that user has. There may however come a time that you want to rebuild one of these index volumes, to do this, simply open the Vault Admin Console, find the Archive that you wish to look at , go to its properties then select the Index Volumes tab.
Right click the volume you wish to rebuild and then hit the Rebuild option. What this will do is delete that selected volume and those after it, and will then rebuild it from that Sequence number. If you then rebuild the 2 nd index volume, it would delete the 3 rd location, and clear the contents of the 2 nd location, it would then start indexing from the lowest Index Sequence Number for that volume and index from there.
The way the index update works is it opens up the Index Metadata and finds the Highest Index Sequence Number and compares to what is in the database for that index. If the Database says it has 20, items that are indexed, but the index has a highest ISN of 10, then it will simply start indexing item 10,, 10, etc until it has completed. Index Repair When an item fails to index, the failure is marked in the database and a file called IndexMissing.
The most common reason for an item being missing from the index is due to something occurring with the storage where the item could not be read, so for instance if it is attempting to index item 10, and the storage goes offline, it will attempt to read the item three times, if it cannot then it marks it as failed to index and then moves on to the next item.
To repair an index, open the vault admin console, expand out the archives list and right click the Archive you wish to have the index repaired for. Then go to the Index Volumes tab. Otherwise if there is a number in there, you can right click and go to Repair Index. What this then does is open the IndexMissing. Note though, if there is a number in Failed Items column but no IndexMissing. If the IndexMissing. What this will then do is scan the index for any missing items and then regenerate the IndexMissing.
Note: that if this is run against legacy Indexes Indexes created by Enterprise Vault 5 and earlier then it is possible for it to mark each item in the index as being missing. Once it is run, it will have updated the Failed Items column and you can attempt to repair the index again.
Keep an eye on the Event Viewer to determine whether items are failing to be recalled, it could be because they are missing from disk, or they could also be corrupt.
Understanding what each operation does and how it interacts with Enterprise Vault is crucial for getting an understanding of how long it will take for the index to be up to date and operational. Generally the quickest to perform are the Repairs, as they have a strict set of items to add to the index within the log files.
Updates are the next quickest, as a healthy index should never be too far behind the highest index sequence number, unless its been offline or failed for a very very long time.
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