Query v$sql_monitor is slow. the execution plan shows ‘Full Table Scan’ on Fixed table ‘X$KESWXMON’.
The fix for 28789533 is first included in:
Oracle APR 2021 DB RU

Since Oracle Database 12.2, due to designing change, it becomes no limitation of max entries of the password file, and the “entries” argument of ‘orapwd’ command is deprecated, and password file is made auto-extensible, and prior to, password file is made auto-extensible ORA-01996 will happen when the number entries in Password file exceeds the “entries” value prior to Even though the “entries” argument is deprecated, no error happens if the user specifies it explicitly on ‘orapwd’ command.

According to the description of the online documentation prior to Oracle Database 12.2, the actual number of allowable entries can be higher than the number of specified entries, because the ‘orapwd’ utility continues to assign password entries until an operating system block is filled. For example, if your operating system block size is 512 bytes, it holds four password entries. The number of password entries allocated is always a multiple of four. When you exceed the allocated number of password entries, you must create a new password file. To avoid this necessity, allocate more entries than you think you will ever need.