tcl.overflow Verb: Access/TCL

tcl.overflow

Command tcl.overflow Verb: Access/TCL
Applicable release versions: AP
Category TCL (746)
Description displays the system overflow table which contains the addresses of available disk frames. All unused frames are available for use by the Spooler, the Pick file system, and process workspace.

The overflow table is kept in the "B-tree" format. Each node in the "B-tree" may contain up to 120 elements.

Legend: (see examples)

"overflow" is the total number of frames available.

"reserve" is the 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-saves.

"blocks" is the number of contiguous blocks of storage.

"b-tree levels" is the number of levels in the b-tree that holds the frame addresses.

"leaves" is the number of leaves (nodes on the final level) on the b-tree. All frame addresses are stored at the "leaf" level.
Syntax overflow {(options}
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 will show the block start and end fids plus the sizes, but 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 which are displayed with the (a or (b options in the final frame and block counts.

n (The letter "n") Activates 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 will be restored in case of a power-loss or full system crash.

t Displays blocks in the "safe" table with an asterisk.
Example
overflow
overflow: 8450 reserve: 1024 blocks: 669 b-tree levels: 2 leaves: 9

This 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 (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
Purpose
Related tcl.ovf
tcl.init-ovf
tcl.rebuild-ovf
tcl.set-runaway-limit
tcl.set-ovf-reserve
tcl.povf_rp
tcl.povf