Optical resources

During the resource estimation phase, the planning team used the formulas in Formulas to determine their optical storage needs. They used the object size and volume estimates that were developed during the business analysis phase (see Table 1). The following assumptions were used for the calculation:

Only the 10 000 detail objects would eventually be written to optical disk.
The optical residence period is 180 calendar days from creation date minus the seven calendar days on DASD.

Table 1 represents the optical resources calculated by the planning team for each of the media types.

Note: The free space available on double-density, quad-density, and 8x-density WORM platters might not match the formatted capacity. The hardware holds a certain percentage of sectors in reserve based on the media type.

Table 1. Optical resource requirements for library resident data
Media	SD WORM²	SD REWR²	DD WORM²	DD REWR²	QD WORM	QD REWR	8x WORM	8x REWR
MB of data to write per workday	625	625	625	625	625	625	625	625
Cartridge capacity for user data in KB	297 983	314 569	620 934 637 041⁴	637 041	1 122 469¹ ⁴ 1 211 012² 1 273 011² ⁴	1 122 468¹ 1 273 011²	1 986 966¹ ⁴ 2 319 786² ⁴ 2 256 268³ 2 526 904³ ⁴	1 986 965¹ 2 319 786²
Disks used per workday	1.059	1.078	0.530	0.539	0.248	0.261	0.136² 0.125³	0.144² 0.132³
Calendar days the data is needed to be library resident	173	173	173	173	173	173	173	173
Cartridges needed to retain library resident data	184	187	92	94	43	45	24² 22³	25² 23³
Slots in the library	144	144	144	144	52 104 156 258	52 104 156 258	52 104 156 258	52 104 156 258
Libraries needed to hold library resident data	2	2	1	1	1	1	1	1
Note: MB = megabyte (1 048 576 bytes) GB = gigabyte (1 073 741 824) bytes SD = single-density DD = double-density QD = quad-density 8x = 8x-density REWR = rewritable media WORM = write-once, read-many ¹For 512-sector media ²For 1024-sector media ³For 2048-sector media ⁴For continuous composite WORM (CCW) media. CCW media values are the same as for REWR media of the same density.