In the ACL of database if there are too many entries, we can create a group to manage ACL, but if the number of entries are too many and the size of members field exceeds 64 KB, some members of group do not get the required access.
Instead of having a single group contain all the entries, split the group in different groups each having something like 200 entries and the final group should be included in the ACL mention. The name of all these groups in the Members field (i.e Create 4 Groups GroupA, Group B, Group C, Group D. each having 200 members.) Now create a Final Group GroupAll, this will include Group A, Group B, Group C and Group D as its members. Include this group in ACL. This can be used in Dblookups also.