Improve Acrolinx score: Update troubleshoot-data-retention-issues-expired-data.md

Author: JasonWHowell

articles/hdinsight/hbase/troubleshoot-data-retention-issues-expired-data.md

@@ -10,7 +10,7 @@ ms.date: 09/14/2023
 
 In HBase cluster, you may decide that you would like to remove data after it ages either to free some storage and save on costs as the older data is no longer needed, either to comply with regulations. When that is needed, you need to set TTL in a table at the ColumnFamily level to expire and automatically delete older data. While TTL can be set as well at cell level, setting it at ColumnFamily level is usually a more convenient option because the ease of administration and because a cell TTL (expressed in ms) can't extend the effective lifetime of a cell beyond a ColumnFamily level TTL setting (expressed in seconds), so only required shorter retention times at cell level could benefit from setting cell level TTL. 
 
-Despite setting TTL, you may notice sometimes that you don't obtain the desired effect, i.e. some data hasn't expired and/or storage size hasn't decreased.
+Despite setting TTL, you may notice sometimes that you don't obtain the desired effect, that is, some data hasn't expired and/or storage size hasn't decreased.
 
 ## Prerequisites
 
@@ -28,7 +28,7 @@ Follow the steps and given commands, open two ssh connections to HBase cluster:
 
 Follow the steps given to understand where is the issue. Start by checking if the behavior occurs for a specific table or for all the tables. If you're unsure whether the issue impacts all the tables or a specific table, just consider as example a specific table name for the start. 
 
-1. Check first that TTL has been configured for ColumnFamily for the target tables. Run following command in the ssh session where you launched HBase shell and observe example and output below. One column family has TTL set to 50 seconds, the other ColumnFamily has no value configured for TTL, thus it appears as "FOREVER" (data in this column family isn't configured to expire).
+1. Check first that TTL has been configured for ColumnFamily for the target tables. Run the following command in the ssh session where you launched HBase shell and observe the output. One column family has TTL set to 50 seconds, the other ColumnFamily has no value configured for TTL, thus it appears as "FOREVER" (data in this column family isn't configured to expire).
 
    ```
    describe 'table_name'
@@ -83,17 +83,17 @@ Follow the steps given to understand where is the issue. Start by checking if th
 
 ### Check the number and size of StoreFiles per table per region after major compaction
 
-1. At this point, the data from MemStore has been written to StoreFile, in storage, but expired data may still exist in one or more of the current StoreFiles. Although minor compactions can help delete some of the expired entries, it is not guaranteed that it removes all of them as minor compaction. It will not select all the StoreFiles for compaction, while major compaction will select all the StoreFiles for compaction in that region. 
+1. At this point, the data from MemStore has been written to StoreFile, in storage, but expired data may still exist in one or more of the current StoreFiles. Although minor compactions can help delete some of the expired entries, it is not guaranteed that it removes all of them as minor compaction. It does not select all the StoreFiles for compaction, while major compaction does select all the StoreFiles for compaction in that region. 
 
-      Also, there's another situation when minor compaction may not remove cells with TTL expired. There's a property named MIN_VERSIONS and it defaults to 0 only (see in the above output from describe 'table_name' the property MIN_VERSIONS=>'0'). If this property is set to 0, the minor compaction will remove the cells with TTL expired. If this value is greater than 0, minor compaction may not remove the cells with TTL expired even if it touches the corresponding file as part of compaction. This property configures the min number of versions of a cell to keep, even if those versions have TTL expired.
+      Also, there's another situation when minor compaction may not remove cells with TTL expired. There's a property named MIN_VERSIONS and it defaults to 0 only (see in the above output from describe 'table_name' the property MIN_VERSIONS=>'0'). If this property is set to 0, the minor compaction removes the cells with TTL expired. If this value is greater than 0, minor compaction may not remove the cells with TTL expired even if it touches the corresponding file as part of compaction. This property configures the min number of versions of a cell to keep, even if those versions have TTL expired.
 
-1. To make sure expired data is also deleted from storage, we need to run a major compaction operation. The major compaction operation, when completed, will leave behind a single StoreFile per region. In HBase shell, run the command to execute a major compaction operation on the table:
+1. To make sure expired data is also deleted from storage, we need to run a major compaction operation. When the major compaction operation completes, it leaves behind a single StoreFile per region. In HBase shell, run the command to execute a major compaction operation on the table:
 
    ```
    major_compact 'table_name'
    ```
 
-1. Depending on the table size, major compaction operation can take some time. Use following command in HBase shell to monitor progress. If the compaction is still running when you execute the following command, you get the output as "MAJOR", but if the compaction is completed, you get the as output "NONE."
+1. Depending on the table size, the major compaction operation can take some time. Use the following command in HBase shell to monitor progress. If the compaction is still running when you execute the following command, you get the output as "MAJOR", but if the compaction is completed, you get the as output "NONE."
 
    ```
    compaction_state 'table_name'
@@ -105,16 +105,16 @@ Follow the steps given to understand where is the issue. Start by checking if th
    hdfs dfs -ls -R /hbase/data/default/table_name/ | grep "column_family_name"
    ```
 
-1. You will notice that an extra StoreFile has been created in addition to previous ones per region per ColumnFamily and after several moments only the last created StoreFile is kept per region per column family.
+1. Notice that an extra StoreFile has been created in addition to previous ones per region per ColumnFamily and after several moments only the last created StoreFile is kept per region per column family.
 
    :::image type="content" border="true" source="media/troubleshoot-data-retention-issues-expired-data/image-4.png" alt-text="Screenshot showing store file as column family.":::
 
-For the example region above, once the extra moments elapse, we can notice that one single StoreFile remained and the size occupied by this file on the storage is reduced as major compaction occurred and at this point any expired data that has not been deleted before(by another major compaction), will be deleted after running current major compaction operation.
+For the example region above, once the extra moments elapse, we can notice that one single StoreFile remains. Also, the size occupied by this file on the storage is reduced due to the major compaction. At this point, any expired data that has not been deleted before (by another major compaction), is soon deleted after the current major compaction operation runs.
 
 :::image type="content" border="true" source="media/troubleshoot-data-retention-issues-expired-data/image-5.png" alt-text="Screenshot showing expired data not deleted.":::
 
 > [!NOTE]
-> For this troubleshooting exercise we triggered the major compaction manually. But in practice, doing that manually for many tables might be time consuming. By default, major compaction is disabled on HDInsight cluster. The main reason for keeping major compaction disabled by default is because the performance of the table operations is impacted when a major compaction is in progress. However, you can enable major compaction by configuring the value for the property hbase.hregion.majorcompaction in ms or can use a cron tab job or another external system to schedule compaction at a time convenient for you, with lower workload.
+> For this troubleshooting exercise, you triggered the major compaction manually. But in practice, doing that manually for many tables is time consuming. By default, major compaction is disabled on HDInsight cluster. The main reason for keeping major compaction disabled by default is due to performance of the table operations is impacted when a major compaction is in progress. However, you can enable major compaction by configuring the value for the property  `hbase.hregion.majorcompaction` in ms or can use a cron tab job or another external system to schedule compaction at a time convenient for you, with lower workload.
 
 ## Next steps