A large quantity of files accumulates in this folder:
C:\ProgramData\Qlik\Sense\Repository\PostgreSQL\9.6\pg_xlog
(9.6 is the Repository version and may change). New files are added every day so that they may fill the entire space in C: drive.
The name of the generated files is an hexadecimal code similar to this: 0000000100000021000000AA. They have all the same size, generally 16 MB .
Environment
- Qlik Sense 2019 and higher
Resolution
This problem can be fixed by bringing some configurations for the Postgres Database back to the default state. Before proceeding, kindly, be sure you that they have not been changed for a specific reason, like troubleshooting.
Please, follow this:
- Log in to the machine where the Qlik Sense PostgreSQL database is installed and open this folder:
C:\ProgramData\Qlik\Sense\Repository\PostgreSQL\9.6.
Notice that 9.6 is the version of the Database and may change according to the Sense release installed.
- Open the postgresql.conf file with a text editor program (notepad++, notepad or similar).
- Check the following entries:
max_wal_size = 1GB : this controls the maximum space reserved for the WAL files. This is not a hard limit. The max_wal_size can be exceeded in some cases, like under heavy load, a failing archive_command, or a high wal_keep_segments setting.
wal_keep_segments = 0 : This is the minimum number of WAL files to keep in the directory. It should be 0 or a small number.
This will re-activate the automatic cleaning process in Postgress. Notice that the setting "archive_mode on" can block the removal of the WAL files cleaning process, even if the parameters above are set correctly. So this must also be removed.
Please, also notice:
- It is not recommended to delete WAL files manualy. This may create problems with the repository starting process.
- It is essential to have enough space in the pg_xlog folder to store the WALs otherwise the DB stops immediately and can't restart until some room is made. Qlik Sense will not be able to work until the Database is running again.
Cause
The hexadecimal named files saved in the folder are called WAL (Write Ahead Log) and are generated by the PostgreSQL Database.
When PostgreSQL is running normally, there is a finite number of WAL files it in the pg_xlog directory. Postgres normally deletes older WAL files automatically, so the total number of files never climbs too high.
By default, the automatic cleaning of WALs is enabled when Sense installs the database. It is possible that some configurations have been manually changed in the database config file if the WALs are not removed by the system.
