mongodb - mongo write lock behavior -

i have question on mongo locks. have perform write operation on table(insert/ delete/ update). when read link locking in mongodb. says "locks “writer greedy,” , when write lock exists, single write operation holds lock exclusively, , no other read or write operations may share lock.

my question -- lock memory block based or have single lock on entire db. thinking concurrently run 2 scripts scanning 2 memory blocks of mongodb (planning scan 2 million documents in 1 query) , perform write operation side side thereby increasing performance , saving time.

i searched on net didnt find satisfactory.

any appreciated

the write lock has nothing memory, mongodb not in-memory database, os merely caches working set of mongod process ram. mongodb has no memory hooks in program.

the write lock on database level such plan not feasible.