For Point-in-Time Recovery (PITR), PostgreSQL must be configured for continuous WAL (Write-Ahead Log) archiving. The wallevel parameter controls the volume of information written to the WAL. In PostgreSQL 13, the minimum level required to write enough data for WAL archiving is replica. This level ensures that all information needed to reconstruct database states for recovery and support read-only standby servers is logged. Setting wallevel to replica or higher (i.e., logical) is a mandatory prerequisite for enabling the archivemode and archivecommand parameters used in PITR setups.

A. wallevel = minimal: This level only logs information sufficient for crash recovery, which is not enough for WAL archiving or PITR.

C. wallevel = archive: This value is obsolete in PostgreSQL 13. It was merged with hotstandby into the replica setting in PostgreSQL 9.6.

D. wallevel = logical: While this level would also enable WAL archiving, it adds extra information for logical decoding, which is not strictly required for PITR. The minimum necessary level is replica.

1. PostgreSQL 13 Official Documentation, Chapter 26. Backup and Restore, Section 26.3.1. Setting Up WAL Archiving.

"To enable WAL archiving, set the wallevel configuration parameter to replica or higher, archivemode to on, and specify the shell command to use in archivecommand." This explicitly states replica as the minimum requirement.

2. PostgreSQL 13 Official Documentation, Chapter 19. Server Configuration, Section 19.5.1. Settings.

"wallevel determines how much information is written to the WAL. The default value is replica. Possible values are minimal, replica, and logical." It further clarifies: "replica writes enough data to support WAL archiving and replication..." and "minimal removes all logging except the information required to recover from a crash or an immediate shutdown."

3. PostgreSQL 13 Official Documentation, Appendix F. Release Notes, Section F.28. Release 9.6.

"Merge wallevel settings archive and hotstandby into a new setting replica (Simon Riggs, Robert Haas)." This confirms that archive is an outdated setting from before version 9.6.