Tag Archives: WAL files

Disable ARCHIVELOG Mode

PostgreSQL, , , , , , , , , , , , , ,

How to Disable ARCHIVELOG Mode

Table of Contents

1. Verify Existing Archive Mode
2. Edit the archive settings
3. Restart PostgreSQL
4. Verify Current Mode
5. Verify WAL Archiving Behavior

1. Verify Existing Archive Mode

postgres=# SHOW archive_mode;
 archive_mode
--------------
 on  <------ 
(1 row)

postgres=#

postgres=# SHOW archive_command;
        archive_command
-------------------------------
 cp %p /pgArch/pgsql17/arch/%f  <----- 
(1 row)

postgres=#

2. Edit the archive settings


[postgres@lxicbpgdsgv01 ~]$ cp /pgData/pgsql17/data/postgresql.conf /pgData/pgsql17/data/postgresql.conf.bkp_10sep2025
[postgres@lxicbpgdsgv01 ~]$ vi /pgData/pgsql17/data/postgresql.conf

#archive_mode = on
#archive_command = 'cp %p /pgArch/pgsql17/arch/%f'

3. Restart PostgreSQL

[root@lxicbpgdsgv01 ~]# systemctl stop postgresql-17.service
[root@lxicbpgdsgv01 ~]#
[root@lxicbpgdsgv01 ~]# systemctl start  postgresql-17.service
[root@lxicbpgdsgv01 ~]#
[root@lxicbpgdsgv01 ~]# systemctl status postgresql-17.service
● postgresql-17.service - PostgreSQL 17 database server
     Loaded: loaded (/usr/lib/systemd/system/postgresql-17.service; enabled; preset: disabled)
     Active: active (running) since Thu 2025-10-09 16:34:01 +08; 3s ago
       Docs: https://www.postgresql.org/docs/17/static/
    Process: 3492 ExecStartPre=/usr/pgsql-17/bin/postgresql-17-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)
   Main PID: 3497 (postgres)
      Tasks: 7 (limit: 15835)
     Memory: 17.6M
        CPU: 92ms
     CGroup: /system.slice/postgresql-17.service
             ├─3497 /usr/pgsql-17/bin/postgres -D /pgData/pgsql17/data/
             ├─3498 "postgres: logger "
             ├─3499 "postgres: checkpointer "
             ├─3500 "postgres: background writer "
             ├─3502 "postgres: walwriter "
             ├─3503 "postgres: autovacuum launcher "
             └─3504 "postgres: logical replication launcher "

Oct 09 16:34:01 lxicbpgdsgv01.rajasekhar.com systemd[1]: Starting PostgreSQL 17 database server...
Oct 09 16:34:01 lxicbpgdsgv01.rajasekhar.com postgres[3497]: 2025-10-09 16:34:01.929 +08 [3497] LOG:  redirecting log output to logging collector process
Oct 09 16:34:01 lxicbpgdsgv01.rajasekhar.com postgres[3497]: 2025-10-09 16:34:01.929 +08 [3497] HINT:  Future log output will appear in directory "log".
Oct 09 16:34:01 lxicbpgdsgv01.rajasekhar.com systemd[1]: Started PostgreSQL 17 database server.
[root@lxicbpgdsgv01 ~]#

4. Verify Current Mode

[postgres@lxicbpgdsgv01 ~]$ psql
psql (17.6)
Type "help" for help.

postgres=# SHOW archive_mode;
 archive_mode
--------------
 off  <------ it's disabled
(1 row)

postgres=# SHOW archive_command;
 archive_command
-----------------
 (disabled) <-------
(1 row)

postgres=#

5. Verify WAL Archiving Behavior


postgres=# CHECKPOINT;
CHECKPOINT
postgres=#
postgres=# CHECKPOINT;
CHECKPOINT
postgres=# CHECKPOINT;
CHECKPOINT
postgres=#
postgres=# exit
postgres=# SELECT pg_switch_wal();
 pg_switch_wal
---------------
 0/44000000
(1 row)

postgres=# SELECT pg_switch_wal();
 pg_switch_wal
---------------
 0/44000000
(1 row)

postgres=# SELECT pg_switch_wal();
 pg_switch_wal
---------------
 0/44000000
(1 row)

postgres=#
[postgres@lxicbpgdsgv01 ~]$ ls -ltr /pgArch/pgsql17/arch/
total 0  <---- Archivelogs not generating
[postgres@lxicbpgdsgv01 ~]$

Caution: Your use of any information or materials on this website is entirely at your own risk. It is provided for educational purposes only. It has been tested internally, however, we do not guarantee that it will work for you. Ensure that you run it in your test environment before using.

Thank you,
Rajasekhar Amudala
Email: br8dba@gmail.com
Linkedin: https://www.linkedin.com/in/rajasekhar-amudala/

WAL Files

PostgreSQL, , , , , , , , , , , , ,

Understanding WAL Files in PostgreSQL – For Oracle DBAs

What is WAL?

WAL (Write-Ahead Logging) ensures data durability and crash recovery. Every change is first written to WAL before being flushed to data files. 

1. WAL Location: WAL files are stored in $PGDATA/pg_wal/.
2. Fixed Size: Each WAL segment is pre-allocated with a fixed size (typically 16MB), set at cluster initialization (initdb).
3. Writing & Switching: WAL segments are written sequentially. PostgreSQL switches to the next segment when the current one is full or a manual switch is triggered (e.g., via pg_switch_wal()).
4. WAL and Archive File Size: When archived, the exact same 16MB WAL segment file is copied as raw binary to the archive destination. Therefore, archive files always match the WAL segment size.
5. Archiving: If archive_mode = on, PostgreSQL uses the archive_command to copy completed WAL segments to the archive destination (e.g., /pgArch/...). Only full segments are archived.
6. Recycling: If archiving is disabled, PostgreSQL reuses old WAL segments once they’re no longer needed for recovery or replication.

WAL Files = Redo Log Files
WAL Archives = Archive Log Files

PostgreSQL vs Oracle Comparison

AspectOraclePostgreSQL
Redo Log FilesCalled Redo Log FilesCalled WAL Files
Archive Log FilesCalled Archive Log FilesCalled WAL Archives
Redo Log File Size~200MB (default)16MB (default and fixed)
Redo Log Files CountMinimum 2 or more redo log groups
(Best practice: 3)		No fixed number
Controlled by: min_wal_size / wal_segment_size
Example: 80MB / 16MB = 5 WAL files
Archive Log File Size~200MB (same as redo log file size)16MB (same as WAL file size)
Log File StorageRedo log files stored in redo log groupsWAL files stored in pg_wal directory
Archiving MechanismArchive logs created if archiving is enabledArchived via archive_command if archive_mode = on
Overwrite BehaviorRedo logs are overwritten when full (if archive not enabled)WAL segments are recycled/overwritten when full (if archive_mode is off)
Force Switch BehaviorALTER SYSTEM SWITCH LOGFILE;SELECT pg_switch_wal();

PostgreSQL WAL Configuration Parameters

ParameterMeaningDefault
wal_segment_sizeSize of each WAL file16MB
min_wal_sizeMinimum total WAL size retained80MB (5 WAL files)
Common in production: 8GB
max_wal_sizeMax WAL before triggering a checkpoint1GB
Common in production: 16GB

Check Configuration

[postgres@lxicbpgdsgv01 ~]$ psql -c "SHOW wal_segment_size;"
wal_segment_size
------------------
16MB  <----- Each redo log file size
(1 row)

[postgres@lxicbpgdsgv01 ~]$


[postgres@lxicbpgdsgv01 ~]$ psql -c "SHOW min_wal_size;"
 min_wal_size
--------------
 80MB <---- 80MB/16MB = 5 <--- Total 5 redo log files with each 16MB
(1 row)

[postgres@lxicbpgdsgv01 ~]$
[postgres@lxicbpgdsgv01 ~]$ psql -c "SHOW max_wal_size;"
 max_wal_size
--------------
 1GB  <---- 1024MB
(1 row)

[postgres@lxicbpgdsgv01 ~]$

View WAL files (Redo log files)

postgres=# SELECT current_setting('data_directory') || '/pg_wal' AS wal_directory;
        wal_directory
-----------------------------
 /pgData/pgsql17/data/pg_wal  <---- Redo log file directory
(1 row)

postgres=# 
[postgres@lxicbpgdsgv01 ~]$ ls -lh /pgData/pgsql17/data/pg_wal | grep -E '^-.* [0-9]+ .* [0-9A-F]{24}$'
-rw-------. 1 postgres postgres 16M Oct 8 01:33 000000010000000000000005
-rw-------. 1 postgres postgres 16M Oct 8 01:28 000000010000000000000006
-rw-------. 1 postgres postgres 16M Oct 8 01:28 000000010000000000000007
[postgres@lxicbpgdsgv01 ~]$

min_wal_size = 80MB means PostgreSQL will try to keep at least 5 WAL segment files on disk (since 80MB ÷ 16MB = 5 files).

However, in our case, only 3 WAL files are currently present. This is likely because the system is under low load in the testing environment, so fewer WAL files are needed at the moment.

---- Lets Generate Load

postgres=# -- Create test table
DROP TABLE IF EXISTS wal_test;
CREATE TABLE wal_test (
    id serial PRIMARY KEY,
    data text
);

-- Generate WAL traffic
DO $$
DECLARE
    i integer;
BEGIN
    FOR i IN 1..50 LOOP
        -- INSERT: 10,000 rows
        INSERT INTO wal_test (data)
        SELECT repeat('wal_test_data_', 50)
        FROM generate_series(1, 10000);

        -- UPDATE: 5,000 rows using CTE with LIMIT
        WITH to_update AS (
            SELECT id FROM wal_test WHERE id % 2 = 0 LIMIT 5000
        )
        UPDATE wal_test
        SET data = data || '_updated'
        WHERE id IN (SELECT id FROM to_update);

        -- DELETE: 5,000 rows using CTE with LIMIT
        WITH to_delete AS (
            SELECT id FROM wal_test WHERE id % 3 = 0 LIMIT 5000
        )
        DELETE FROM wal_test
        WHERE id IN (SELECT id FROM to_delete);

        -- Commit to flush WAL
        COMMIT;

        -- Optional pause to slow down the loop
        PERFORM pg_sleep(0.5);
    END LOOP;
END$$;
DROP TABLE
CREATE TABLE
DO
postgres=# exit
[postgres@lxicbpgdsgv01 ~]$
[postgres@lxicbpgdsgv01 ~]$ 
ls -lrth /pgData/pgsql17/data/pg_wal
total 752M
drwx------. 2 postgres postgres    6 Sep 30 21:50 summaries
-rw-------. 1 postgres postgres  16M Oct  8 16:34 000000010000000000000009
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000A
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000B
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000C
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000D
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000E
-rw-------. 1 postgres postgres  16M Oct  8 16:34 00000001000000000000000F
-rw-------. 1 postgres postgres  16M Oct  8 16:34 000000010000000000000010
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000011
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000012
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000013
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000014
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000015
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000016
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000017
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000018
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000019
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001A
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001B
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001C
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001D
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001E
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000001F
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000020
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000021
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000022
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000023
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000024
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000025
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000026
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000027
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000028
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000029
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002A
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002B
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002C
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002D
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002E
-rw-------. 1 postgres postgres  16M Oct  8 16:35 00000001000000000000002F
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000030
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000031
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000032
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000033
-rw-------. 1 postgres postgres  16M Oct  8 16:35 000000010000000000000034
-rw-------. 1 postgres postgres  16M Oct  8 16:36 000000010000000000000035
drwx------. 2 postgres postgres 4.0K Oct  8 16:36 archive_status
-rw-------. 1 postgres postgres  16M Oct  8 16:36 xlogtemp.7289
[postgres@lxicbpgdsgv01 ~]$ 

-- Now We can see Many WAL Files (Redo log files) generated, count increased from 3 WAL files to 50+ WAL files

View Archived WAL Files (Archive log files)

postgres=# SHOW archive_command;
        archive_command
-------------------------------
 cp %p /pgArch/pgsql17/arch/%f
(1 row)

postgres=#

[postgres@lxicbpgdsgv01 ~]$ 
[postgres@lxicbpgdsgv01 ~]$ ls -lrth /pgArch/pgsql17/arch/
total 976M
-rw-------. 1 postgres postgres 16M Oct  7 23:50 000000010000000000000001
-rw-------. 1 postgres postgres 16M Oct  7 23:51 000000010000000000000002
-rw-------. 1 postgres postgres 16M Oct  8 01:28 000000010000000000000003
-rw-------. 1 postgres postgres 16M Oct  8 01:28 000000010000000000000004
-rw-------. 1 postgres postgres 16M Oct  8 04:24 000000010000000000000005
-rw-------. 1 postgres postgres 16M Oct  8 16:08 000000010000000000000006
-rw-------. 1 postgres postgres 16M Oct  8 16:24 000000010000000000000007
-rw-------. 1 postgres postgres 16M Oct  8 16:25 000000010000000000000008
-rw-------. 1 postgres postgres 16M Oct  8 16:34 000000010000000000000009
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000A
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000B
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000C
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000D
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000E
-rw-------. 1 postgres postgres 16M Oct  8 16:34 00000001000000000000000F
-rw-------. 1 postgres postgres 16M Oct  8 16:34 000000010000000000000010
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000011
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000012
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000013
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000014
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000015
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000016
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000017
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000018
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000019
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001A
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001B
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001C
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001D
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001E
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000001F
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000020
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000021
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000022
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000023
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000024
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000025
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000026
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000027
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000028
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000029
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002A
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002B
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002C
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002D
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002E
-rw-------. 1 postgres postgres 16M Oct  8 16:35 00000001000000000000002F
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000030
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000031
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000032
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000033
-rw-------. 1 postgres postgres 16M Oct  8 16:35 000000010000000000000034
-rw-------. 1 postgres postgres 16M Oct  8 16:36 000000010000000000000035
-rw-------. 1 postgres postgres 16M Oct  8 16:36 000000010000000000000036
-rw-------. 1 postgres postgres 16M Oct  8 16:36 000000010000000000000037
-rw-------. 1 postgres postgres 16M Oct  8 16:36 000000010000000000000038
-rw-------. 1 postgres postgres 16M Oct  8 16:36 000000010000000000000039
-rw-------. 1 postgres postgres 16M Oct  8 16:36 00000001000000000000003A
-rw-------. 1 postgres postgres 16M Oct  8 16:36 00000001000000000000003B
-rw-------. 1 postgres postgres 16M Oct  8 16:36 00000001000000000000003C
-rw-------. 1 postgres postgres 16M Oct  8 16:36 00000001000000000000003D
[postgres@lxicbpgdsgv01 ~]$

-- WAL and Archive File Size: When archived, the exact same 16MB WAL segment file is copied as raw binary to the archive destination. Therefore, archive files always match the WAL segment size (redo log size).

Best Practices

  • Use a dedicated mount point for pg_wal (WAL directory) – eg. /pgWal
  • Set min_wal_size to higher value in production (e.g. 8GB)
  • Keep WAL archive files on a separate mount point for better I/O and space isolation – eg. /pgArch
  • Monitor WAL archive directory regularly to avoid disk full errors

Note:

  • WAL file size is fixed at cluster init (default: 16MB). You cannot change it for an existing cluster.
  • PostgreSQL WAL Size Be Can Increased only at NEW cluster creation time via initdb (64MB)
    /usr/pgsql-17/bin/initdb –wal-segsize=64 -D /pgData/pgsql17/data

Caution: Your use of any information or materials on this website is entirely at your own risk. It is provided for educational purposes only. It has been tested internally, however, we do not guarantee that it will work for you. Ensure that you run it in your test environment before using.

Thank you,
Rajasekhar Amudala
Email: br8dba@gmail.com
Linkedin: https://www.linkedin.com/in/rajasekhar-amudala/

Enable Archive Mode (WAL Archiving)

PostgreSQL, , , , , , , , , , , , , , ,

Enable Archive Mode in PostgreSQL 17

Table of Contents

0. Importance of Archive Log Files
1. Verify Existing Archive Mode
2. Ensure Archive Directory Exists
3. Edit postgresql.conf
4. Restart PostgreSQL
5. Verify the Configuration
6. Test Archiving Works

0. Importance of Archive Log Files

Archive log files, also known as WAL archives (Write-Ahead Log archives) , play a critical role in PostgreSQL for data protection, recovery, and replication.

A. Point-in-Time Recovery (PITR): Restore the database to a specific point in time, useful for accidental data changes or loss.
B. Continuous Backup: Works with base backups to enable robust disaster recovery.
C. Streaming Replication Support: Helps standby servers catch up if they fall behind.
D. Disaster Recovery: Enables full recovery after hardware or data corruption.
E. Data Audit & Analysis: Allows decoding WAL logs for auditing and compliance.

🛑 Important Note:

If WAL archiving is disabled and a backup is taken, you can only restore to the exact backup time, not to any point after.

1. Verify Existing Archive Mode

[postgres@lxicbpgdsgv01 ~]$ psql
psql (17.6)
Type "help" for help.

postgres=# SHOW archive_mode;
 archive_mode 
--------------
 off <--- it's off
(1 row)

postgres=# SHOW archive_command;
 archive_command 
-----------------
 (disabled) <----
(1 row)
[root@lxicbpgdsgv01 ~]# systemctl status postgresql-17
● postgresql-17.service - PostgreSQL 17 database server
     Loaded: loaded (/usr/lib/systemd/system/postgresql-17.service; enabled; preset: disabled)
     Active: active (running) since Tue 2025-10-07 18:33:05 +08; 2min 26s ago
       Docs: https://www.postgresql.org/docs/17/static/
    Process: 5911 ExecStartPre=/usr/pgsql-17/bin/postgresql-17-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)
   Main PID: 5916 (postgres)
      Tasks: 7 (limit: 15700)
     Memory: 21.3M
        CPU: 177ms
     CGroup: /system.slice/postgresql-17.service
             ├─5916 /usr/pgsql-17/bin/postgres -D /pgData/pgsql17/data/
             ├─5917 "postgres: logger "
             ├─5918 "postgres: checkpointer "
             ├─5919 "postgres: background writer "
             ├─5921 "postgres: walwriter "
             ├─5922 "postgres: autovacuum launcher "
             └─5923 "postgres: logical replication launcher "

Oct 07 18:33:05 lxicbpgdsgv01.rajasekhar.com systemd[1]: Starting PostgreSQL 17 database server...
Oct 07 18:33:05 lxicbpgdsgv01.rajasekhar.com postgres[5916]: 2025-10-07 18:33:05.392 +08 [5916] LOG:  redirecting log output to logging collector process
Oct 07 18:33:05 lxicbpgdsgv01.rajasekhar.com postgres[5916]: 2025-10-07 18:33:05.392 +08 [5916] HINT:  Future log output will appear in directory "log".
Oct 07 18:33:05 lxicbpgdsgv01.rajasekhar.com systemd[1]: Started PostgreSQL 17 database server.
[root@lxicbpgdsgv01 ~]#

Currently, there is no active archive process running in the background.

2. Ensure Archive Directory Exists

[root@lxicbpgdsgv01 ~]# mkdir -p /pgArch/pgsql17/arch/
[root@lxicbpgdsgv01 ~]# chown postgres:postgres /pgArch/pgsql17/arch/
[root@lxicbpgdsgv01 ~]# chmod 700 /pgArch/pgsql17/arch/

3. Edit postgresql.conf

[postgres@lxicbpgdsgv01 ~]$ vi /pgData/pgsql17/data/postgresql.conf

Update or add the following lines:

archive_mode = on
archive_command = 'cp %p /pgArch/pgsql17/arch/%f'

Explanation:

  • %p = Full path of WAL file
  • %f = WAL file name
  • cp %p /pgArch/pgsql17/arch/%f = Command to copy the WAL file to archive directory

4. Restart PostgreSQL

[root@lxicbpgdsgv01 ~]# systemctl status postgresql-17
● postgresql-17.service - PostgreSQL 17 database server
     Loaded: loaded (/usr/lib/systemd/system/postgresql-17.service; enabled; preset: disabled)
     Active: active (running) since Tue 2025-10-07 23:48:29 +08; 18s ago
       Docs: https://www.postgresql.org/docs/17/static/
    Process: 7868 ExecStartPre=/usr/pgsql-17/bin/postgresql-17-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)
   Main PID: 7873 (postgres)
      Tasks: 8 (limit: 15700)
     Memory: 19.0M
        CPU: 96ms
     CGroup: /system.slice/postgresql-17.service
             ├─7873 /usr/pgsql-17/bin/postgres -D /pgData/pgsql17/data/
             ├─7874 "postgres: logger "
             ├─7875 "postgres: checkpointer "
             ├─7876 "postgres: background writer "
             ├─7878 "postgres: walwriter "
             ├─7879 "postgres: autovacuum launcher "
             ├─7880 "postgres: archiver "  <------
             └─7881 "postgres: logical replication launcher "

Oct 07 23:48:29 lxicbpgdsgv01.rajasekhar.com systemd[1]: Starting PostgreSQL 17 database server...
Oct 07 23:48:29 lxicbpgdsgv01.rajasekhar.com postgres[7873]: 2025-10-07 23:48:29.503 +08 [7873] LOG:  redirecting log output to logging collector process
Oct 07 23:48:29 lxicbpgdsgv01.rajasekhar.com postgres[7873]: 2025-10-07 23:48:29.503 +08 [7873] HINT:  Future log output will appear in directory "log".
Oct 07 23:48:29 lxicbpgdsgv01.rajasekhar.com systemd[1]: Started PostgreSQL 17 database server.
[root@lxicbpgdsgv01 ~]#

Make sure the archiver process is running.

5. Verify the Configuration

[postgres@lxicbpgdsgv01 ~]$ psql -c "SHOW archive_mode;"
 archive_mode 
--------------
 on <-----------
(1 row)

[postgres@lxicbpgdsgv01 ~]$ psql -c "SHOW archive_command;"
        archive_command         
-------------------------------
 cp %p /pgArch/pgsql17/arch/%f  <-----------------
(1 row)

6. Test Archiving Works

[postgres@lxicbpgdsgv01 ~]$ psql -c "SELECT pg_switch_wal();"

Check archive folder for new WAL files:

[postgres@lxicbpgdsgv01 ~]$ ls -lrth /pgArch/pgsql17/arch/
total 16M
-rw-------. 1 postgres postgres 16M Oct  7 23:50 000000010000000000000001

[postgres@lxicbpgdsgv01 ~]$ psql -c "SELECT pg_switch_wal();"
[postgres@lxicbpgdsgv01 ~]$ ls -lrth /pgArch/pgsql17/arch/
total 32M
-rw-------. 1 postgres postgres 16M Oct  7 23:50 000000010000000000000001
-rw-------. 1 postgres postgres 16M Oct  7 23:51 000000010000000000000002

 Archiving is working successfully.

Caution: Your use of any information or materials on this website is entirely at your own risk. It is provided for educational purposes only. It has been tested internally, however, we do not guarantee that it will work for you. Ensure that you run it in your test environment before using.

Thank you,
Rajasekhar Amudala
Email: br8dba@gmail.com
Linkedin: https://www.linkedin.com/in/rajasekhar-amudala/