An operation fails in Plesk with a blank page or one of the following error messages in Plesk:
PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 16384 bytes) in /path/to/plesk/file.php on line 228
Out of memory (allocated 23855104) (tried to allocate 12975879 bytes) (Abstract.php:41)
Memory limit is exceeded by Plesk PHP back-end. This may happen if an object, over which the operation is performed, has a complex structure.