AIX系统安装之后，默认不允许单个文件大小超过2G，对于企业应用系统来说，这个限制一般是需要去除的。
首先，取消安全方面的限制，需要修改配置文件/etc/security/limits，可以针对所有用户在default段修改，或者在指定user段来修改具体user的限制。下面是一个示例。设置成－1，表示取消大小限制。
cat /etc/security/limits
*
* Sizes are in multiples of 512 byte blocks, CPU time is in seconds
*
* fsize - soft file size in blocks
* core - soft core file size in blocks
* cpu - soft per process CPU time limit in seconds
* data - soft data segment size in blocks
* stack - soft stack segment size in blocks
* rss - soft real memory usage in blocks
* nofiles - soft file descriptor limit
* fsize_hard - hard file size in blocks
* core_hard - hard core file size in blocks
* cpu_hard - hard per process CPU time limit in seconds
* data_hard - hard data segment size in blocks
* stack_hard - hard stack segment size in blocks
* rss_hard - hard real memory usage in blocks
* nofiles_hard - hard file descriptor limit
*
* The following table contains the default hard values if the
* hard values are not explicitly defined:
*
* Attribute Value
* ========== ============
* fsize_hard set to fsize
* cpu_hard set to cpu
* core_hard -1
* data_hard -1
* stack_hard 8388608
* rss_hard -1
* nofiles_hard -1
*
* NOTE: A value of -1 implies "unlimited"
*
default:
fsize = -1
core = 2097151
cpu = -1
data = -1
rss = -1
stack = -1
nofiles = 65536
maxuprc =1024
root:
daemon:
bin:
sys:
adm:
uucp:
guest:
nobody:
lpd:
oracle:
fsize = -1
core = 2097151
cpu = -1
data = -1
rss = -1
stack = -1
nofiles = 65536
除了安全方面的限制，单个文件大小还受文件系统类型的限制，AIX下主要使用JFS和JFS2文件系统，下面是一个对比表格。可见，JFS最大只能支持64G的单个文件，有时候做大文件的归档备份时，有可能会超过这个限制的，所以建议使用JFS2文件系统。
| Functions | JFS2 | JFS |
|---|---|---|
| Fragments/Block Size | 512-4096 Block sizes | 512-4096 Frags |
| Maximum file system size | 16 Terabytes | 1 Terabyte |
| Maximum file size | 16 Terabytes | 64 GB |
| Number of i-nodes | Dynamic, limited by disk space | Fixed, set at file-system creation |
| Directory organization | B-tree | Linear |
| Compression | No | Yes |
| Quotas | No | Yes |
| Error logging | Yes | Yes |