What are the functions of the files in the fdb data directory?

Using FoundationDB
1

I searched the relevant documents and found no analysis of the functions of these files. Who can help me? Thank you.

4501]# ll
total 229452
-rw---S--- 1 foundationdb foundationdb 104857600 Oct 20 14:56 log2-V_6-a8680cf4d8afb5f3d34d7cc92ab6977c.sqlite
-rw---S--- 1 foundationdb foundationdb     28672 Oct 20 14:56 log2-V_6-a8680cf4d8afb5f3d34d7cc92ab6977c.sqlite-wal
-rw---S--- 1 foundationdb foundationdb  24043520 Oct 20 14:56 logqueue-V_6-a8680cf4d8afb5f3d34d7cc92ab6977c-0.fdq
-rw---S--- 1 foundationdb foundationdb   1138688 Oct 20 13:50 logqueue-V_6-a8680cf4d8afb5f3d34d7cc92ab6977c-1.fdq
-rw---S--- 1 foundationdb foundationdb      4096 Oct 19 14:36 processId
-rw---S--- 1 foundationdb foundationdb 104857600 Oct 20 14:56 storage-6697fd036e4779716f3c2ee0729c821b.sqlite
-rw---S--- 1 foundationdb foundationdb     28672 Oct 20 14:56 storage-6697fd036e4779716f3c2ee0729c821b.sqlite-wal

4500]# ll
total 118016
-rw---S--- 1 foundationdb foundationdb     28672 Oct 19 15:36 coordination-0.fdq
-rw---S--- 1 foundationdb foundationdb     65536 Oct 19 15:36 coordination-1.fdq
-rw---S--- 1 foundationdb foundationdb      4096 Oct 19 14:36 processId
-rw---S--- 1 foundationdb foundationdb 104857600 Oct 20 14:58 storage-3aff38f2d99acec7dd0167e43ec9ceb1.sqlite
-rw---S--- 1 foundationdb foundationdb  15892480 Oct 20 14:58 storage-3aff38f2d99acec7dd0167e43ec9ceb1.sqlite-wal

I know that *.sqlite is a file that stores data. What are the functions of files *.fdq and processId?

Thanks!