1. Identify the source of the PostgreSQL 23001 error:

SELECT * FROM pg_stat_activity;

2. Check the PostgreSQL log file for more information about the error:

tail -f /var/log/postgresql/postgresql-9.6-main.log

3. Check the PostgreSQL configuration file for any misconfigurations:

cat /etc/postgresql/9.6/main/postgresql.conf

4. Check the PostgreSQL system tables for any inconsistencies:

SELECT * FROM pg_class;

5. Check the PostgreSQL system views for any inconsistencies:

SELECT * FROM pg_views;

6. Check the PostgreSQL system functions for any inconsistencies:

SELECT * FROM pg_proc;

7. Check the PostgreSQL system triggers for any inconsistencies:

SELECT * FROM pg_trigger;

8. Check the PostgreSQL system indexes for any inconsistencies:

SELECT * FROM pg_index;

9. Check the PostgreSQL system constraints for any inconsistencies:

SELECT * FROM pg_constraint;

10. Check the PostgreSQL system roles for any inconsistencies:

SELECT * FROM pg_roles;

11. Check the PostgreSQL system databases for any inconsistencies:

SELECT * FROM pg_database;

12. Check the PostgreSQL system tablespaces for any inconsistencies:

SELECT * FROM pg_tablespace;

13. Check the PostgreSQL system extensions for any inconsistencies:

SELECT * FROM pg_extension;

14. Check the PostgreSQL system settings for any inconsistencies:

SELECT * FROM pg_settings;

15. Check the PostgreSQL system statistics for any inconsistencies:

SELECT * FROM pg_statistic;

16. Check the PostgreSQL system locks for any inconsistencies:

SELECT * FROM pg_locks;

17. Check the PostgreSQL system user mappings for any inconsistencies:

SELECT * FROM pg_user_mappings;

18. Check the PostgreSQL system foreign data wrappers for any inconsistencies:

SELECT * FROM pg_foreign_data_wrappers;

19. Check the PostgreSQL system foreign servers for any inconsistencies:

SELECT * FROM pg_foreign_server;

20. Check the PostgreSQL system foreign tables for any inconsistencies:

SELECT * FROM pg_foreign_table;

21. Check the PostgreSQL system large objects for any inconsistencies:

SELECT * FROM pg_largeobject;

22. Check the PostgreSQL system resource queues for any inconsistencies:

SELECT * FROM pg_resqueue;

23. Check the PostgreSQL system resource groups for any inconsistencies:

SELECT * FROM pg_resgroup;

24. Check the PostgreSQL system resource group members for any inconsistencies:

SELECT * FROM pg_resgroupmember;

25. Check the PostgreSQL system resource group capabilities for any inconsistencies:

SELECT * FROM pg_resgroupcapability;

26. Check the PostgreSQL system resource group limits for any inconsistencies:

SELECT * FROM pg_resgrouplimit;

27. Check the PostgreSQL system resource group roles for any inconsistencies:

SELECT * FROM pg_resgrouprole;

28. Check the PostgreSQL system resource group settings for any inconsistencies:

SELECT * FROM pg_resgroupsetting;

29. Check the PostgreSQL system resource group mappings for any inconsistencies:

SELECT * FROM pg_resgroupmapping;

30. Check the PostgreSQL system resource group privileges for any inconsistencies:

SELECT * FROM pg_resgroupprivilege;

31. Check the PostgreSQL system resource group quotas for any inconsistencies:

SELECT * FROM pg_resgroupquota;

32. Check the PostgreSQL system resource group options for any inconsistencies:

SELECT * FROM pg_resgroupoption;

33. Check the PostgreSQL system resource group categories for any inconsistencies:

SELECT * FROM pg_resgroupcategory;

34. Check the PostgreSQL system resource group categories limits for any inconsistencies:

SELECT * FROM pg_resgroupcategorylimit;

35. Check the PostgreSQL system resource group categories roles for any inconsistencies:

SELECT * FROM pg_resgroupcategoryrole;

36. Check the PostgreSQL system resource group categories settings for any inconsistencies:

SELECT * FROM pg_resgroupcategorysetting;

37. Check the PostgreSQL system resource group categories privileges for any inconsistencies:

SELECT * FROM pg_resgroupcategoryprivilege;

38. Check the PostgreSQL system resource group categories quotas for any inconsistencies:

SELECT * FROM pg_resgroupcategoryquota;

39. Check the PostgreSQL system resource group categories options for any inconsistencies:

SELECT * FROM pg_resgroupcategoryoption;

40. Finally, use an automated database observability tool to monitor and fix the PostgreSQL 23001 in question. Automated database observability tools can provide real-time insights into the performance and health of your PostgreSQL database, allowing you to quickly identify and address any issues that may arise. This can help you proactively prevent errors like PostgreSQL 23001 from occurring in the future.