There are several techniques and best practices for database index maintenance. Rebuilding indexes should be done online. This is better than offline. You can also process databases one at a time. Rebuilding clustered columnstore indexes is the best way to optimize performance. This article outlines some of the best practices for maintaining columnstore indexes. Read on to find out more. Here are some more tips:
Online index rebuilding is better than offline index rebuilding
Online index rebuilding is better than offline index building for a number of reasons. Online rebuilds minimize downtime by running index operations while the database is online. Offline index rebuilds require heavy locking of tables, resulting in blocking issues for other database users. However, you can delay the impact of blocking by using the WAIT_AT_LOW_PRIORITY option. But be aware that online index rebuilding is not available for LOB columns.
While index rebuilding may be faster than offline, there are several disadvantages. Large indexes take longer to rebuild because they generate more log, thereby impacting performance more. Another problem is that large indexes cannot be automatically REBUILD. Instead, they need to be manually reorganized, which can take a very long time. This is like waiting for paint to dry! To make index rebuilding faster, you should investigate how to speed up the communication process.
Another major difference between offline and online index rebuilding is the transaction log. Online index rebuilds generate minimal transaction log, whereas offline index rebuilds always generate full logs. As a result, the next log backup contains the extents changed during rebuilding. And if you need to perform a large data change, you should go for offline index rebuilding. This saves time and transaction log, but the cost is in the reorganization process.
If you choose to perform an online index rebuild, you will need to pause the indexing operation while it is in progress. You can also use the pause command to interrupt the indexing operation while it is in progress. This pauses the indexing operation, allowing you to make your changes to the target index. A few other advantages of online index rebuilding over offline index rebuilding are:
Process databases one at a time
One of the most important index maintenance best practices is to reorganize your indexes. This method uses minimal system resources while defragmenting your indexes. This method is best suited for indexes with fragmentation levels below 20 percent. However, you should note that this method only reorganizes index pages at the leaf level. As a result, index statistics will not be updated.
While this option increases database performance, it can be inefficient. Indexes may be created for a specific query, which may not be needed for the database at that time. If you no longer need an index, remove it from your database to reduce maintenance overhead. Databases change and use data over time, and indexes need to evolve to match those changes. High performance index maintenance is all about keeping your indexes up to date with changing data usage.
It is important to understand the benefits of index maintenance, as it will cause a significant increase in CPU, memory, and storage I/O. Its benefits, however, vary depending on workload and other factors, and you should not perform index maintenance on indiscriminately. For each workload, you should measure the benefits of index maintenance empirically. The benefits must be weighed against the resources required and workload impact.
Using the “IndexOptimize” feature allows you to set a lower threshold for medium and high fragmentation. By default, the lower limit is 100. If you set the value below that, SQL Server will use two pages for index maintenance and allocate empty space. In this way, you can use the “Process databases one at a time” option. It will also skip index maintenance if you have a large number of rows or columns.
Reorganize nonclustered indexes
When a database fragments, reorganizing an index is a best practice. This process physically reorganizes index leaf nodes to match the nodes below them. Then, it compacts the index pages, so that the overall index size is less than the original. While the reorganize process can grow an index substantially, the size of the resulting index depends on the amount of reorganization performed and the level of fragmentation.
After creating a clustered index, performing a reorganization of nonclustered indexes is especially crucial. When building a clustered index, SQL Server must also rebuild nonclustered indexes. After the clustering, it rebuilds all indexes to point to the clustered index’s key. In addition, it provides an index maintenance area to run index rebuilds.
When building an index on a large table, you may want to rebuild it. This option improves query performance but introduces a performance hit. In addition, it may lock the table so that no one else can change it. In such a case, you can use Query Store to measure the performance of your queries. This way, you can identify a problem with your index and take steps to solve it.
If you have fragmented indexes, reorganizing them is the best solution. This process reorganizes index rows into the correct physical order. When the reorganization is completed, you can resume index rebuilding or suspend it. The process does not lock the affected indexed table. You can perform this operation while the index is online. You may not get 100% fragmentation reduction, but the index will still be more efficient.
Rebuild clustered columnstore indexes
When rebuilding a clustered columnstore index, you’re doing more than restoring the structure of a single table. Rebuilding this type of index can also improve segment elimination. The space occupied by deleted or updated rows is reclaimed and all rows are compressed into as few rowgroups as possible. Database index maintenance best practices include rebuilding clustered columnstore indexes periodically during workloads that involve updating data and loading processes that compress rowgroups.
Columnstore indexes should be rebuilt with the same care as OLTP tables. This way, they’ll continue to perform well even when exposed to large volumes of data. Furthermore, it will make it easier to upgrade and release software. However, there are some disadvantages to columnstore indexes. For example, the size of the memory-optimized data will be roughly double that of the disk-based columnstore index.
Another advantage of columnstore indexes is that they can be stored natively in memory. For example, if you used classic B-tree indexes, your table was five gigabytes. While this might not seem like a lot, consider how much your data would increase in size over the course of a year! This is not trivial, but a 100MB columnstore index would use minimal memory.
When rebuilding clustered columnstore indexes, you can change the compression level of the single columnstore partition. In addition to reducing the size, you can specify how much parallelism the cluster uses. Generally, you can choose between standard and archive columnstore compression. You can also specify the number of nodes used for the rebuild. If you use a standard compression level, it’s fine.
Repair nonclustered index inconsistencies
If you encounter the error, it is best to take the affected data from backup and rebuild the nonclustered index offline. The problem with rebuilding online is that the repair mechanism uses the existing nonclustered index, which will carry over the inconsistency. Repairing offline is more effective since the process forces a scan of both clustered and heap indexes.
Corrupted data can corrupt the entire table. In such a case, the table definition needs to be recreated. After rebuilding the nonclustered index, the table may need data populating again. If this is not possible, perform a manual rebuild. Using these techniques will help you avoid data loss. But make sure to carefully investigate the cause of the corruption so that you can find the right solution for the problem.
One way to improve query performance is to rebuild the index. While this approach can lead to higher database resource utilization, it also has the added benefit of improving query performance. Aside from the obvious benefits, this maintenance technique reduces the workload and resources. Unlike index rebuilding, updating statistics is less expensive and can be performed in a matter of minutes instead of hours. Query Store is a great way to measure the performance of queries.
After rebuilding the nonclustered index, check the Fill Factor. If the Fill Factor is 80%, the index rebuild maintenance plan should be 20% or less. This will yield pages that have 80% free space. The free space per page is stored in the instance’s Server Properties. You can access this property by right-clicking the instance name and selecting Properties. Then, follow the steps in the script to fix the index.
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