Hi,
Sometimes You can get “ORA-12531: TNS:cannot allocate memory ” error.
Details of error are as follows.
ORA-12531: TNS:cannot allocate memory
Cause: Sufficient memory could not be allocated to perform the desired activity.
Action: Either free some resource for TNS, or add more memory to the machine.
For further details, turn on tracing and reexecute the operation.
This error is related with database server was a 32-Bit Windows machine where maximum 4G RAM can be utilized. Once all RAM is consumed.
Or Check hostname definition if it is different from the /etc/hosts file or not.
Do you want to learn more details about RMAN, then read the following articles.
https://ittutorial.org/rman-backup-restore-and-recovery-tutorials-for-beginners-in-the-oracle-database/