X_EXPORT_PART_TOO_LARGE

one page encoded to more bytes than a part may hold

a page whose encoded size passed maxPartBytes (default 8 MiB). The memory bound made mechanical: accumulating a result set before writing it is the failure exportRows() exists to prevent, and "we hold a page, not a dataset" is only true while a page is bounded — a row that is a megabyte of JSON turns a thousand-row page into a gigabyte in one buffer

lower batch on exportRows("<name>") until a page fits (the default is 500 rows), or raise maxPartBytes if this deployment really can hold that much per part — the number is a heap bound, not a file-size preference