Remove PREFIX_TREE data block encoding

Before upgrading to CDP Private Cloud Base, you must ensure that you have transitioned all the data to a supported encoding type.

If your cluster is Kerberized, ensure that you run the kinit command as a hbase user before running the pre-upgrade commands.
Ensure you have valid Kerberos credentials. You can list the Kerberos credentials using the klist command, and you can obtain credentials using the kinit command.

Use the hbase pre-upgrade validate-dbe command to identify HFiles using the PREFIX_TREE data block encoding.

Run the hbase pre-upgrade validate-dbe command on the cluster that has the HDP intermediate bits.
For example, if you are using the HDP 7.1.2.0-96 intermediate bits, you must run the following command:
```
/usr/hdp/7.1.2.0-96/hbase/bin/hbase pre-upgrade validate-dbe
```
The commands check whether your table or snapshots use the PREFIX_TREE data block encoding. This command does not take much time to run because it validates only the table-level descriptors.
If the HFiles do not use PREFIX_TREE data block encoding, the following message is displayed:
```
The used Data Block Encodings are compatible with HBase 2.0.
```
If you see this message, your data block encodings are compatible, and you do not have to do any more steps.
If an HFile uses the PREFIX_TREE data block encoding, a similar error message to the following is displayed:
```
2018-07-13 09:58:32,028 WARN  [main] tool.DataBlockEncodingValidator: Incompatible DataBlockEncoding for table: t, cf: f, encoding: PREFIX_TREE
```
If you see this error message, continue to Step 2 and fix all your PREFIX_TREE encoded tables.
Fix your PREFIX_TREE encoded tables using the old installation.
You can change the Data Block Encoding type to PREFIX, DIFF, or FAST_DIFF in your source cluster.

For example, if your validation output reported column family f of table t is invalid. Its Data Block Encoding type is changed to FAST_DIFF:
```
hbase> alter 't', { NAME => 'f', DATA_BLOCK_ENCODING => 'FAST_DIFF' }
```
1. Run the following command on the cluster that has the HDP intermediate bits.
```
hbase pre-upgrade validate-hfile
```
  note
  This command checks every HFile (including snapshots) to ensure none of the HFile have PREFIX_TREE data block encoding. It opens every HFile, so this operation can take a long time.
  If there is no HFile with PREFIX_TREE encoding, a confirmation message similar to the following is displayed:
```
Checked n HFiles, none of them are corrupted. 
There are no incompatible HFiles.
```
  If you have an HFile with PREFIX_TREE encoding, an error message similar to the following is displayed:
```
INFO  [main] tool.HFileContentValidator: Corrupted file: hdfs://example.com:8020/hbase/data/default/t/72ea7f7d625ee30f959897d1a3e2c350/prefix/7e6b3d73263c4851bf2b8590a9b3791e
2018-06-05 16:20:47,383 INFO  [main] tool.HFileContentValidator: Corrupted file: hdfs://example.com:8020/hbase/archive/data/default/t/56be41796340b757eb7fff1eb5e2a905/f/29c641ae91c34fc3bee881f45436b6d1
```
  If the error message is displayed, go to the next step. If you don't see an error, skip to Validate HFile.
2. Get the table name from the output. Our example output showed the /hbase/data/default/t/… file path, which means that the HFile belongs to the t table which is in the default namespace.
3. Rewrite the HFiles by running major compaction in the old installation using this command.
```
hbase > major_compact 't'
```
  When the major compaction is complete, the original invalid HFile is automatically removed.
4. Run the hbase pre-upgrade validate-hfile command again to confirm if all the HFiles are rewritten in the new encoding format.

Validate HFile