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A quota is a limit imposed by the system manager with an aim to control resources available to processes on the system. Quota usually refers to disk quota, a method for maintaining and enforcing limits on the amount of disk space available to users on a public volume.

Disk quotas

On each volume or volume set where disk quotas are enabled, including private ones, a quota file is maintained that contains disk quota values for different users. A volume on which quotas are not maintained has no quota file. On a volume set, volume 1 contains the quota file. The quota file is maintained using the SYSMAN utility by users holding the OPER privilege.

Disk quotas on a volume can be enabled with the SYSMAN DISKQUOTA CREATE command.

If users run out of disk space during the creation of a file, they receive a system message. The system manager sets up quotas and overdraft limits. Users who have reached their quota but haven't reached the overdraft limit may not create new files but may expand existing ones. Users who have reached the overdraft limit may not create new files or expand existing ones. Users who attempt to write a file to a spooled printer must have write access and have sufficient quota on the disk associated with that printer.

A quota file has the following format:

   UIC (1)         Usage (2)       Permanent Quota (3)  Overdraft Limit (4)
[0,0]             0               333333              3333 
[TTD,DAVIS]       15590           333333              3333 
[TTD,MORGAN]      1929            333333              3333 
[MKT,MORSE]       7650            333333              3333 


Quota restrictions are not enforced for users with the EXQUOTA privilege; however, their usage counts are maintained. Users with no entries in the quota file are not allowed to create files on that volume (unless they have the EXQUOTA privilege.

Process Quotas

Limits that can be imposed on a process include:

See also