The overflow command displays the system overflow table which contains the addresses of available disk frames. All unused frames are available for use by the spooler, the D3 file system, and the process workspace.
overflow {(options}
ovf povf
| options | a | Lists the start and end FIDs for each block as well as their sizes. When using the (a option, the user may filter the FIDs displayed by specifying a high and low limit. If the (b option is used along with the (a option, then the display shows the block start and end FIDs plus the sizes. The user can filter blocks based on size. |
| b | Lists total number of frames for each contiguous block of overflow. When using the (b option, the user may specify a range of sizes as well. | |
| c | Only counts frames that display with the (a or (b options in the final frame and block counts. | |
| n | Activates the nopage function on output to the terminal. | |
| o | Displays the old safe table. Before every full or incremental save, the most significant blocks in the overflow table are saved in an alternate area. This area can be displayed using the (o option. This option is useful for analyzing the change in overflow over a time period. | |
| p | Directs output to the printer via the spooler. | |
| s | Displays only safe blocks. The safe blocks are blocks that are restored in case of a power loss or full system crash. | |
| t | Displays blocks in the safe table with an asterisk. |
The overflow table is kept in the B-tree format. Each node in the B-tree may contain up to 120 elements.
The report includes the following headings:
| overflow | Total number of frames available. |
| reserve | Number of frames held in reserve (must have been previously established with the set-ovf-reserve command). These frames are used only when all overflow frames have been used and are intended to provide space on an emergency basis for system functions such as file-save commands. |
| blocks | Number of contiguous blocks of storage. |
| B-tree levels | Number of levels in the B-tree that holds the frame addresses. |
| leaves | Number of leaves (nodes on the final level) on the B-tree. All frame addresses are stored at the leaf level. |
Indicates that there are 8450 frames remaining in the overflow table, 1024 marked as the spare gas tank; a total of 669 blocks in the table; 2 B-tree levels with 9 leaves.
overflow overflow: 8450 reserve: 1024 blocks: 669 b-tree levels: 2 leaves: 9
overflow (a319843-319934 319838-319844 : 7 319849-319855 : 7 319866-319866 : 1 319885-319885 : 1 319889-319889 : 1 319898-319899 : 2 319902-319902 : 1 319907-319909 : 3 319924-319924 : 1 319927-319927 : 1 319929-319929 : 1 319932-319932 : 1 319934-319934 : 1 overflow: 8497 reserve: 1024 blocks: 692 b-tree levels: 2 leaves: 9