Hi Tiago,
Since the table /POSDW/TLOGS contains all the transaction logs of POS sales, it is usual for it to grow in size while accommodating daily sales data.
You can use /POSDW/DELE to delete tlogs and /POSDW/DELE to delete aggregates from the table.
More over, you can try option of achieving using tcode sara (Arch object /POSDW/TL) to archive and delete the sales data.
Regards,
Mrigaya