]>
Commit | Line | Data |
---|---|---|
fea681da | 1 | .\" Copyright 1995 Robert K. Nichols (Robert.K.Nichols@att.com) |
e2af0daf | 2 | .\" Copyright 1999-2005 Kai Mäkisara (Kai.Makisara@kolumbus.fi) |
fea681da | 3 | .\" |
4b72fb64 | 4 | .\" %%%LICENSE_START(verbatim) |
fea681da MK |
5 | .\" Permission is granted to make and distribute verbatim copies of this |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of this | |
10 | .\" manual under the conditions for verbatim copying, provided that the | |
11 | .\" entire resulting derived work is distributed under the terms of a | |
12 | .\" permission notice identical to this one. | |
e2af0daf | 13 | .\" |
fea681da MK |
14 | .\" Since the Linux kernel and libraries are constantly changing, this |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
16 | .\" responsibility for errors or omissions, or for damages resulting from | |
17 | .\" the use of the information contained herein. The author(s) may not | |
18 | .\" have taken the same level of care in the production of this manual, | |
19 | .\" which is licensed free of charge, as they might when working | |
20 | .\" professionally. | |
e2af0daf | 21 | .\" |
fea681da MK |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 24 | .\" %%%LICENSE_END |
72542487 | 25 | .TH ST 4 2010-09-04 "Linux" "Linux Programmer's Manual" |
fea681da MK |
26 | .SH NAME |
27 | st \- SCSI tape device | |
28 | .SH SYNOPSIS | |
29 | .nf | |
30 | .B #include <sys/mtio.h> | |
31 | .sp | |
32 | .BI "int ioctl(int " fd ", int " request " [, (void *)" arg3 "]);" | |
e40c76c0 MK |
33 | .BI "int ioctl(int " fd ", MTIOCTOP, (struct mtop *)" mt_cmd ); |
34 | .BI "int ioctl(int " fd ", MTIOCGET, (struct mtget *)" mt_status ); | |
35 | .BI "int ioctl(int " fd ", MTIOCPOS, (struct mtpos *)" mt_pos ); | |
fea681da MK |
36 | .fi |
37 | .SH DESCRIPTION | |
38 | The | |
39 | .B st | |
40 | driver provides the interface to a variety of SCSI tape devices. | |
41 | Currently, the driver takes control of all detected devices of type | |
cba04495 | 42 | \(lqsequential-access\(rq. |
fea681da MK |
43 | The |
44 | .B st | |
45 | driver uses major device number 9. | |
46 | .PP | |
c13182ef MK |
47 | Each device uses eight minor device numbers. |
48 | The lowermost five bits | |
fea681da | 49 | in the minor numbers are assigned sequentially in the order of |
c13182ef MK |
50 | detection. |
51 | In the 2.6 kernel, the bits above the eight lowermost bits are | |
e51d6af5 | 52 | concatenated to the five lowermost bits to form the tape number. |
e2af0daf | 53 | The minor numbers can be grouped into |
fea681da MK |
54 | two sets of four numbers: the principal (auto-rewind) minor device numbers, |
55 | .IR n , | |
e2af0daf | 56 | and the \(lqno-rewind\(rq device numbers, |
cba04495 | 57 | .RI ( n " + 128)." |
fea681da | 58 | Devices opened using the principal device number will be sent a |
e40c76c0 MK |
59 | .BR REWIND |
60 | command when they are closed. | |
fea681da MK |
61 | Devices opened using the \(lqno-rewind\(rq device number will not. |
62 | (Note that using an auto-rewind device for positioning the tape with, | |
63 | for instance, mt does not lead to the desired result: the tape is | |
64 | rewound after the mt command and the next command starts from the | |
65 | beginning of the tape). | |
66 | .PP | |
67 | Within each group, four minor numbers are available to define | |
68 | devices with different characteristics (block size, compression, | |
c13182ef MK |
69 | density, etc.) |
70 | When the system starts up, only the first device is available. | |
71 | The other three are activated when the default | |
6387216b MK |
72 | characteristics are defined (see below). |
73 | (By changing compile-time | |
fea681da MK |
74 | constants, it is possible to change the balance between the maximum |
75 | number of tape drives and the number of minor numbers for each | |
c13182ef MK |
76 | drive. |
77 | The default allocation allows control of 32 tape drives. | |
fea681da MK |
78 | For instance, it is possible to control up to 64 tape drives |
79 | with two minor numbers for different options.) | |
80 | .PP | |
81 | Devices are typically created by: | |
a6e2f128 | 82 | .in +4n |
fea681da | 83 | .nf |
cf0a9ace | 84 | |
2bc2f479 MK |
85 | mknod \-m 666 /dev/st0 c 9 0 |
86 | mknod \-m 666 /dev/st0l c 9 32 | |
87 | mknod \-m 666 /dev/st0m c 9 64 | |
88 | mknod \-m 666 /dev/st0a c 9 96 | |
89 | mknod \-m 666 /dev/nst0 c 9 128 | |
90 | mknod \-m 666 /dev/nst0l c 9 160 | |
91 | mknod \-m 666 /dev/nst0m c 9 192 | |
92 | mknod \-m 666 /dev/nst0a c 9 224 | |
fea681da | 93 | .fi |
a6e2f128 | 94 | .in |
fea681da MK |
95 | .PP |
96 | There is no corresponding block device. | |
97 | .PP | |
98 | The driver uses an internal buffer that has to be large enough to hold | |
c13182ef MK |
99 | at least one tape block. |
100 | In kernels before 2.1.121, the buffer is | |
101 | allocated as one contiguous block. | |
102 | This limits the block size to the | |
fea681da | 103 | largest contiguous block of memory the kernel allocator can provide. |
e2af0daf | 104 | The limit is currently 128 kB for 32-bit architectures and |
c13182ef MK |
105 | 256 kB for 64-bit architectures. |
106 | In newer kernels the driver | |
107 | allocates the buffer in several parts if necessary. | |
108 | By default, the | |
109 | maximum number of parts is 16. | |
110 | This means that the maximum block size | |
fea681da MK |
111 | is very large (2 MB if allocation of 16 blocks of 128 kB succeeds). |
112 | .PP | |
113 | The driver's internal buffer size is determined by a compile-time | |
114 | constant which can be overridden with a kernel startup option. | |
115 | In addition to this, the driver tries to allocate a larger temporary | |
cf50118f | 116 | buffer at run time if necessary. |
c13182ef | 117 | However, run-time allocation of large |
fea681da MK |
118 | contiguous blocks of memory may fail and it is advisable not to rely |
119 | too much on dynamic buffer allocation with kernels older than 2.1.121 | |
120 | (this applies also to demand-loading the driver with kerneld or kmod). | |
121 | .PP | |
122 | The driver does not specifically support any tape drive brand or | |
c13182ef MK |
123 | model. |
124 | After system start-up the tape device options are defined by | |
e2af0daf MK |
125 | the drive firmware. |
126 | For example, if the drive firmware selects fixed-block mode, | |
c13182ef MK |
127 | the tape device uses fixed-block mode. |
128 | The options can | |
fea681da | 129 | be changed with explicit |
5e21af3a | 130 | .BR ioctl (2) |
fea681da | 131 | calls and remain in effect when the device is closed and reopened. |
24b74457 | 132 | Setting the options affects both the auto-rewind and the nonrewind |
fea681da MK |
133 | device. |
134 | .PP | |
135 | Different options can be specified for the different devices within | |
c13182ef MK |
136 | the subgroup of four. |
137 | The options take effect when the device is | |
138 | opened. | |
139 | For example, the system administrator can define | |
e2af0daf MK |
140 | one device that writes in fixed-block mode with a certain block size, |
141 | and one which writes in variable-block mode (if the drive supports | |
fea681da MK |
142 | both modes). |
143 | .PP | |
144 | The driver supports | |
145 | .B tape partitions | |
c13182ef MK |
146 | if they are supported by the drive. |
147 | (Note that the tape partitions | |
148 | have nothing to do with disk partitions. | |
149 | A partitioned tape can be | |
150 | seen as several logical tapes within one medium.) | |
151 | Partition support has to be enabled with an | |
5e21af3a | 152 | .BR ioctl (2). |
1e321034 | 153 | The tape |
fea681da MK |
154 | location is preserved within each partition across partition changes. |
155 | The partition used for subsequent tape operations is | |
c13182ef | 156 | selected with an |
5e21af3a | 157 | .BR ioctl (2). |
1e321034 | 158 | The partition switch is executed together with |
fea681da | 159 | the next tape operation in order to avoid unnecessary tape |
c13182ef MK |
160 | movement. |
161 | The maximum number of partitions on a tape is defined by a | |
162 | compile-time constant (originally four). | |
163 | The driver contains an | |
5e21af3a | 164 | .BR ioctl (2) |
1e321034 | 165 | that can format a tape with either one or two partitions. |
fea681da MK |
166 | .PP |
167 | Device | |
8478ee02 | 168 | .I /dev/tape |
fea681da MK |
169 | is usually created as a hard or soft link to the default tape device |
170 | on the system. | |
e2af0daf MK |
171 | .PP |
172 | Starting from kernel 2.6.2, the driver exports in the sysfs directory | |
0daa9e92 | 173 | .I /sys/class/scsi_tape |
e2af0daf | 174 | the attached devices and some parameters assigned to the devices. |
73d8cece | 175 | .SS Data transfer |
e2af0daf MK |
176 | The driver supports operation in both fixed-block mode and |
177 | variable-block mode (if supported by the drive). | |
178 | In fixed-block mode the drive | |
fea681da | 179 | writes blocks of the specified size and the block size is not |
e2af0daf MK |
180 | dependent on the byte counts of the write system calls. |
181 | In variable-block mode one tape block is written for each write call | |
182 | and the byte | |
c13182ef MK |
183 | count determines the size of the corresponding tape block. |
184 | Note that | |
e2af0daf | 185 | the blocks on the tape don't contain any information about the |
fea681da MK |
186 | writing mode: when reading, the only important thing is to use |
187 | commands that accept the block sizes on the tape. | |
188 | .PP | |
e2af0daf | 189 | In variable-block mode the read byte count does not have to match |
c13182ef MK |
190 | the tape block size exactly. |
191 | If the byte count is larger than the | |
fea681da | 192 | next block on tape, the driver returns the data and the function |
c13182ef MK |
193 | returns the actual block size. |
194 | If the block size is larger than the | |
fea681da MK |
195 | byte count, the requested amount of data from the start of the block |
196 | is returned and the rest of the block is discarded. | |
197 | .PP | |
e2af0daf | 198 | In fixed-block mode the read byte counts can be arbitrary if |
fea681da | 199 | buffering is enabled, or a multiple of the tape block size if |
c13182ef MK |
200 | buffering is disabled. |
201 | Kernels before 2.1.121 allow writes with | |
202 | arbitrary byte count if buffering is enabled. | |
203 | In all other cases | |
fea681da MK |
204 | (kernel before 2.1.121 with buffering disabled or newer kernel) the |
205 | write byte count must be a multiple of the tape block size. | |
206 | .PP | |
e2af0daf | 207 | In the 2.6 kernel, the driver tries to use direct transfers between the user |
c13182ef MK |
208 | buffer and the device. |
209 | If this is not possible, the driver's internal buffer | |
210 | is used. | |
211 | The reasons for not using direct transfers include improper alignment | |
e2af0daf MK |
212 | of the user buffer (default is 512 bytes but this can be changed by the HBA |
213 | driver), one of more pages of the user buffer not reachable by the | |
214 | SCSI adapter, etc. | |
215 | .PP | |
fea681da MK |
216 | A filemark is automatically written to tape if the last tape operation |
217 | before close was a write. | |
218 | .PP | |
219 | When a filemark is encountered while reading, the following | |
c13182ef MK |
220 | happens. |
221 | If there are data remaining in the buffer when the filemark | |
222 | is found, the buffered data is returned. | |
223 | The next read returns zero | |
224 | bytes. | |
225 | The following read returns data from the next file. | |
226 | The end of | |
fea681da | 227 | recorded data is signaled by returning zero bytes for two consecutive |
c13182ef MK |
228 | read calls. |
229 | The third read returns an error. | |
2b2581ee | 230 | .SS Ioctls |
c13182ef | 231 | The driver supports three |
5e21af3a | 232 | .BR ioctl (2) |
1e321034 | 233 | requests. |
fea681da MK |
234 | Requests not recognized by the |
235 | .B st | |
236 | driver are passed to the | |
237 | .B SCSI | |
238 | driver. | |
239 | The definitions below are from | |
8478ee02 | 240 | .IR /usr/include/linux/mtio.h : |
73d8cece | 241 | .SS MTIOCTOP \(em perform a tape operation |
fea681da MK |
242 | .PP |
243 | This request takes an argument of type | |
8478ee02 | 244 | .IR "(struct mtop *)" . |
fea681da | 245 | Not all drives support all operations. |
a9b4ebbc MK |
246 | The driver returns an |
247 | .B EIO | |
248 | error if the drive rejects an operation. | |
fea681da | 249 | .PP |
088a639b | 250 | .in +4n |
fea681da | 251 | .nf |
e40c76c0 | 252 | /* Structure for MTIOCTOP \- mag tape op command: */ |
fea681da | 253 | struct mtop { |
cf0a9ace MK |
254 | short mt_op; /* operations defined below */ |
255 | int mt_count; /* how many of them */ | |
fea681da MK |
256 | }; |
257 | .fi | |
e40c76c0 | 258 | .in |
fea681da MK |
259 | .PP |
260 | Magnetic Tape operations for normal tape use: | |
e40c76c0 | 261 | .TP 14 |
e40c76c0 | 262 | .B MTBSF |
fea681da | 263 | Backward space over |
f19a0f03 | 264 | .I mt_count |
fea681da | 265 | filemarks. |
e40c76c0 MK |
266 | .TP |
267 | .B MTBSFM | |
fea681da | 268 | Backward space over |
f19a0f03 | 269 | .I mt_count |
fea681da MK |
270 | filemarks. |
271 | Reposition the tape to the EOT side of the last filemark. | |
e40c76c0 MK |
272 | .TP |
273 | .B MTBSR | |
fea681da | 274 | Backward space over |
f19a0f03 | 275 | .I mt_count |
fea681da | 276 | records (tape blocks). |
e40c76c0 MK |
277 | .TP |
278 | .B MTBSS | |
fea681da | 279 | Backward space over |
f19a0f03 | 280 | .I mt_count |
fea681da | 281 | setmarks. |
e40c76c0 MK |
282 | .TP |
283 | .B MTCOMPRESSION | |
fea681da | 284 | Enable compression of tape data within the drive if |
f19a0f03 | 285 | .I mt_count |
c7094399 | 286 | is nonzero and disable compression if |
f19a0f03 | 287 | .I mt_count |
c13182ef MK |
288 | is zero. |
289 | This command uses the MODE page 15 supported by most DATs. | |
e40c76c0 MK |
290 | .TP |
291 | .B MTEOM | |
fea681da | 292 | Go to the end of the recorded media (for appending files). |
e40c76c0 MK |
293 | .TP |
294 | .B MTERASE | |
c13182ef MK |
295 | Erase tape. |
296 | With 2.6 kernel, short erase (mark tape empty) is performed if the | |
297 | argument is zero. | |
298 | Otherwise long erase (erase all) is done. | |
e40c76c0 MK |
299 | .TP |
300 | .B MTFSF | |
fea681da | 301 | Forward space over |
f19a0f03 | 302 | .I mt_count |
fea681da | 303 | filemarks. |
e40c76c0 MK |
304 | .TP |
305 | .B MTFSFM | |
fea681da | 306 | Forward space over |
f19a0f03 | 307 | .I mt_count |
fea681da MK |
308 | filemarks. |
309 | Reposition the tape to the BOT side of the last filemark. | |
e40c76c0 MK |
310 | .TP |
311 | .B MTFSR | |
fea681da | 312 | Forward space over |
f19a0f03 | 313 | .I mt_count |
fea681da | 314 | records (tape blocks). |
e40c76c0 MK |
315 | .TP |
316 | .B MTFSS | |
fea681da | 317 | Forward space over |
f19a0f03 | 318 | .I mt_count |
fea681da | 319 | setmarks. |
e40c76c0 MK |
320 | .TP |
321 | .B MTLOAD | |
c13182ef MK |
322 | Execute the SCSI load command. |
323 | A special case is available for some HP | |
324 | autoloaders. | |
325 | If | |
f19a0f03 | 326 | .I mt_count |
08362d55 MK |
327 | is the constant |
328 | .B MT_ST_HPLOADER_OFFSET | |
329 | plus a number, the number is | |
fea681da | 330 | sent to the drive to control the autoloader. |
e40c76c0 MK |
331 | .TP |
332 | .B MTLOCK | |
fea681da | 333 | Lock the tape drive door. |
e40c76c0 MK |
334 | .TP |
335 | .B MTMKPART | |
c13182ef MK |
336 | Format the tape into one or two partitions. |
337 | If | |
f19a0f03 | 338 | .I mt_count |
c7094399 | 339 | is nonzero, it gives the size of the first partition and the second |
c13182ef MK |
340 | partition contains the rest of the tape. |
341 | If | |
f19a0f03 | 342 | .I mt_count |
fea681da MK |
343 | is zero, the tape is formatted into one partition. |
344 | This command is not allowed for a drive unless the partition support | |
e40c76c0 MK |
345 | is enabled for the drive (see |
346 | .BR MT_ST_CAN_PARTITIONS | |
347 | below). | |
348 | .TP | |
349 | .B MTNOP | |
5503c85e | 350 | No op\(emflushes the driver's buffer as a side effect. |
979c2c91 | 351 | Should be used before reading status with |
e40c76c0 MK |
352 | .BR MTIOCGET . |
353 | .TP | |
354 | .B MTOFFL | |
fea681da | 355 | Rewind and put the drive off line. |
e40c76c0 MK |
356 | .TP |
357 | .B MTRESET | |
fea681da | 358 | Reset drive. |
e40c76c0 MK |
359 | .TP |
360 | .B MTRETEN | |
3f1c1b0a | 361 | Re-tension tape. |
e40c76c0 MK |
362 | .TP |
363 | .B MTREW | |
fea681da | 364 | Rewind. |
e40c76c0 MK |
365 | .TP |
366 | .B MTSEEK | |
fea681da | 367 | Seek to the tape block number specified in |
f19a0f03 | 368 | .IR mt_count . |
e40c76c0 MK |
369 | This operation requires either a SCSI-2 drive that supports the |
370 | .B LOCATE | |
fea681da MK |
371 | command (device-specific address) |
372 | or a Tandberg-compatible SCSI-1 drive (Tandberg, Archive | |
e40c76c0 | 373 | Viper, Wangtek, ...). |
fea681da | 374 | The block number should be one that was previously returned by |
e40c76c0 MK |
375 | .BR MTIOCPOS |
376 | if device-specific addresses are used. | |
377 | .TP | |
378 | .B MTSETBLK | |
fea681da | 379 | Set the drive's block length to the value specified in |
f19a0f03 | 380 | .IR mt_count . |
fea681da | 381 | A block length of zero sets the drive to variable block size mode. |
e40c76c0 MK |
382 | .TP |
383 | .B MTSETDENSITY | |
fea681da | 384 | Set the tape density to the code in |
f19a0f03 | 385 | .IR mt_count . |
fea681da MK |
386 | The density codes supported by a drive can be found from the drive |
387 | documentation. | |
e40c76c0 MK |
388 | .TP |
389 | .B MTSETPART | |
fea681da | 390 | The active partition is switched to |
f19a0f03 | 391 | .IR mt_count . |
c13182ef MK |
392 | The partitions are numbered from zero. |
393 | This command is not allowed for | |
fea681da | 394 | a drive unless the partition support is enabled for the drive (see |
e40c76c0 MK |
395 | .B MT_ST_CAN_PARTITIONS |
396 | below). | |
397 | .TP | |
398 | .B MTUNLOAD | |
fea681da | 399 | Execute the SCSI unload command (does not eject the tape). |
e40c76c0 MK |
400 | .TP |
401 | .B MTUNLOCK | |
fea681da | 402 | Unlock the tape drive door. |
e40c76c0 MK |
403 | .TP |
404 | .B MTWEOF | |
e2af0daf | 405 | Write |
f19a0f03 | 406 | .I mt_count |
fea681da | 407 | filemarks. |
e40c76c0 MK |
408 | .TP |
409 | .B MTWSM | |
fea681da | 410 | Write |
f19a0f03 | 411 | .I mt_count |
fea681da | 412 | setmarks. |
fea681da MK |
413 | .PP |
414 | Magnetic Tape operations for setting of device options (by the superuser): | |
e40c76c0 MK |
415 | .TP 8 |
416 | .B MTSETDRVBUFFER | |
fea681da | 417 | Set various drive and driver options according to bits encoded in |
f19a0f03 | 418 | .IR mt_count . |
e2af0daf | 419 | These consist of the drive's buffering mode, a set of Boolean driver |
fea681da | 420 | options, the buffer write threshold, defaults for the block size and |
74aace8a | 421 | density, and timeouts (only in kernels 2.1 and later). |
fea681da MK |
422 | A single operation can affect only one item in the list above (the |
423 | Booleans counted as one item.) | |
fea681da MK |
424 | .IP |
425 | A value having zeros in the high-order 4 bits will be used to set the | |
426 | drive's buffering mode. | |
427 | The buffering modes are: | |
428 | .RS 12 | |
429 | .IP 0 4 | |
979c2c91 | 430 | The drive will not report |
e40c76c0 MK |
431 | .BR GOOD |
432 | status on write commands until the data | |
fea681da | 433 | blocks are actually written to the medium. |
fea681da | 434 | .IP 1 |
979c2c91 | 435 | The drive may report |
e40c76c0 MK |
436 | .BR GOOD |
437 | status on write commands as soon as all the | |
fea681da MK |
438 | data has been transferred to the drive's internal buffer. |
439 | .IP 2 | |
979c2c91 | 440 | The drive may report |
e40c76c0 MK |
441 | .BR GOOD |
442 | status on write commands as soon as (a) all | |
fea681da MK |
443 | the data has been transferred to the drive's internal buffer, and |
444 | (b) all buffered data from different initiators has been successfully | |
445 | written to the medium. | |
fea681da | 446 | .RE |
e40c76c0 | 447 | .IP |
fea681da | 448 | To control the write threshold the value in |
f19a0f03 | 449 | .I mt_count |
fea681da | 450 | must include the constant |
e40c76c0 | 451 | .BR MT_ST_WRITE_THRESHOLD |
87f6d861 | 452 | bitwise ORed with a block count in the low 28 bits. |
fea681da MK |
453 | The block count refers to 1024-byte blocks, not the physical block |
454 | size on the tape. | |
455 | The threshold cannot exceed the driver's internal buffer size (see | |
e40c76c0 | 456 | DESCRIPTION, above). |
fea681da MK |
457 | .IP |
458 | To set and clear the Boolean options | |
459 | the value in | |
f19a0f03 | 460 | .I mt_count |
e40c76c0 MK |
461 | must include one of the constants |
462 | .BR MT_ST_BOOLEANS , | |
979c2c91 | 463 | .BR MT_ST_SETBOOLEANS , |
e40c76c0 MK |
464 | .BR MT_ST_CLEARBOOLEANS , |
465 | or | |
466 | .BR MT_ST_DEFBOOLEANS | |
87f6d861 | 467 | bitwise ORed with |
fea681da | 468 | whatever combination of the following options is desired. |
e40c76c0 MK |
469 | Using |
470 | .BR MT_ST_BOOLEANS | |
471 | the options can be set to the values | |
c13182ef | 472 | defined in the corresponding bits. |
e40c76c0 MK |
473 | With |
474 | .BR MT_ST_SETBOOLEANS | |
979c2c91 | 475 | the options can be selectively set and with |
e40c76c0 | 476 | .BR MT_ST_DEFBOOLEANS |
fea681da MK |
477 | selectively cleared. |
478 | .IP "" | |
479 | The default options for a tape device are set with | |
e40c76c0 | 480 | .BR MT_ST_DEFBOOLEANS . |
24b74457 | 481 | A nonactive tape device (e.g., device with |
fea681da | 482 | minor 32 or 160) is activated when the default options for it are |
c13182ef MK |
483 | defined the first time. |
484 | An activated device inherits from the device | |
fea681da MK |
485 | activated at start-up the options not set explicitly. |
486 | .IP "" | |
487 | The Boolean options are: | |
fea681da | 488 | .RS |
979c2c91 | 489 | .TP |
e40c76c0 | 490 | .BR MT_ST_BUFFER_WRITES " (Default: true)" |
e2af0daf | 491 | Buffer all write operations in fixed-block mode. |
fea681da MK |
492 | If this option is false and the drive uses a fixed block size, then |
493 | all write operations must be for a multiple of the block size. | |
ae03dc66 | 494 | This option must be set false to write reliable multivolume archives. |
ddf54565 | 495 | .TP |
e40c76c0 | 496 | .BR MT_ST_ASYNC_WRITES " (Default: true)" |
e2af0daf | 497 | When this option is true, write operations return immediately without |
fea681da MK |
498 | waiting for the data to be transferred to the drive if the data fits |
499 | into the driver's buffer. | |
500 | The write threshold determines how full the buffer must be before a | |
501 | new SCSI write command is issued. | |
502 | Any errors reported by the drive will be held until the next | |
503 | operation. | |
ae03dc66 | 504 | This option must be set false to write reliable multivolume archives. |
e40c76c0 MK |
505 | .TP |
506 | .BR MT_ST_READ_AHEAD " (Default: true)" | |
fea681da | 507 | This option causes the driver to provide read buffering and |
e2af0daf | 508 | read-ahead in fixed-block mode. |
fea681da MK |
509 | If this option is false and the drive uses a fixed block size, then |
510 | all read operations must be for a multiple of the block size. | |
e40c76c0 MK |
511 | .TP |
512 | .BR MT_ST_TWO_FM " (Default: false)" | |
fea681da MK |
513 | This option modifies the driver behavior when a file is closed. |
514 | The normal action is to write a single filemark. | |
515 | If the option is true the driver will write two filemarks and | |
516 | backspace over the second one. | |
fea681da MK |
517 | .IP |
518 | Note: | |
519 | This option should not be set true for QIC tape drives since they are | |
520 | unable to overwrite a filemark. | |
521 | These drives detect the end of recorded data by testing for blank tape | |
c13182ef MK |
522 | rather than two consecutive filemarks. |
523 | Most other current drives also | |
fea681da MK |
524 | detect the end of recorded data and using two filemarks is usually |
525 | necessary only when interchanging tapes with some other systems. | |
e40c76c0 MK |
526 | .TP |
527 | .BR MT_ST_DEBUGGING " (Default: false)" | |
fea681da | 528 | This option turns on various debugging messages from the driver |
e40c76c0 MK |
529 | (effective only if the driver was compiled with |
530 | .B DEBUG | |
c7094399 | 531 | defined nonzero). |
e40c76c0 MK |
532 | .TP |
533 | .BR MT_ST_FAST_EOM " (Default: false)" | |
979c2c91 | 534 | This option causes the |
e40c76c0 MK |
535 | .B MTEOM |
536 | operation to be sent directly to the | |
fea681da MK |
537 | drive, potentially speeding up the operation but causing the driver to |
538 | lose track of the current file number normally returned by the | |
e40c76c0 MK |
539 | .B MTIOCGET |
540 | request. | |
541 | If | |
542 | .B MT_ST_FAST_EOM | |
543 | is false the driver will respond to an | |
544 | .B MTEOM | |
545 | request by forward spacing over files. | |
979c2c91 | 546 | .TP |
e40c76c0 | 547 | .BR MT_ST_AUTO_LOCK " (Default: false)" |
fea681da MK |
548 | When this option is true, the drive door is locked when the device is |
549 | opened and unlocked when it is closed. | |
979c2c91 | 550 | .TP |
e40c76c0 | 551 | .BR MT_ST_DEF_WRITES " (Default: false)" |
fea681da MK |
552 | The tape options (block size, mode, compression, etc.) may change |
553 | when changing from one device linked to a drive to another device | |
554 | linked to the same drive depending on how the devices are | |
c13182ef MK |
555 | defined. |
556 | This option defines when the changes are enforced by the | |
fea681da | 557 | driver using SCSI-commands and when the drives auto-detection |
c13182ef MK |
558 | capabilities are relied upon. |
559 | If this option is false, the driver | |
560 | sends the SCSI-commands immediately when the device is changed. | |
561 | If the | |
fea681da | 562 | option is true, the SCSI-commands are not sent until a write is |
c13182ef MK |
563 | requested. |
564 | In this case the drive firmware is allowed to detect the | |
fea681da MK |
565 | tape structure when reading and the SCSI-commands are used only to |
566 | make sure that a tape is written according to the correct specification. | |
979c2c91 | 567 | .TP |
e40c76c0 | 568 | .BR MT_ST_CAN_BSR " (Default: false)" |
fea681da MK |
569 | When read-ahead is used, the tape must sometimes be spaced backward to the |
570 | correct position when the device is closed and the SCSI command to | |
5fab2e7c | 571 | space backward over records is used for this purpose. |
c13182ef | 572 | Some older |
fea681da | 573 | drives can't process this command reliably and this option can be used |
c13182ef MK |
574 | to instruct the driver not to use the command. |
575 | The end result is that, | |
e2af0daf | 576 | with read-ahead and fixed-block mode, the tape may not be correctly |
c13182ef MK |
577 | positioned within a file when the device is closed. |
578 | With 2.6 kernel, the | |
e2af0daf | 579 | default is true for drives supporting SCSI-3. |
e40c76c0 MK |
580 | .TP |
581 | .BR MT_ST_NO_BLKLIMS " (Default: false)" | |
582 | Some drives don't accept the | |
583 | .B "READ BLOCK LIMITS" | |
584 | SCSI command. | |
585 | If this is used, the driver does not use the command. | |
c13182ef | 586 | The drawback is |
fea681da MK |
587 | that the driver can't check before sending commands if the selected |
588 | block size is acceptable to the drive. | |
e40c76c0 MK |
589 | .TP |
590 | .BR MT_ST_CAN_PARTITIONS " (Default: false)" | |
fea681da | 591 | This option enables support for several partitions within a |
c13182ef MK |
592 | tape. |
593 | The option applies to all devices linked to a drive. | |
e40c76c0 MK |
594 | .TP |
595 | .BR MT_ST_SCSI2LOGICAL " (Default: false)" | |
fea681da MK |
596 | This option instructs the driver to use the logical block addresses |
597 | defined in the SCSI-2 standard when performing the seek and tell | |
e40c76c0 MK |
598 | operations (both with |
599 | .B MTSEEK | |
600 | and | |
601 | .B MTIOCPOS | |
602 | commands and when changing tape | |
c13182ef MK |
603 | partition). |
604 | Otherwise the device-specific addresses are used. | |
fea681da | 605 | It is highly advisable to set this option if the drive supports the |
c13182ef MK |
606 | logical addresses because they count also filemarks. |
607 | There are some | |
fea681da | 608 | drives that only support the logical block addresses. |
979c2c91 | 609 | .TP |
e40c76c0 | 610 | .BR MT_ST_SYSV " (Default: false)" |
fea681da | 611 | When this option is enabled, the tape devices use the SystemV |
c13182ef MK |
612 | semantics. |
613 | Otherwise the BSD semantics are used. | |
614 | The most important | |
fea681da | 615 | difference between the semantics is what happens when a device used |
80b50848 | 616 | for reading is closed: in System V semantics the tape is spaced forward |
fea681da | 617 | past the next filemark if this has not happened while using the |
c13182ef MK |
618 | device. |
619 | In BSD semantics the tape position is not changed. | |
979c2c91 | 620 | .TP |
e40c76c0 | 621 | .BR MT_NO_WAIT " (Default: false)" |
e2af0daf MK |
622 | Enables immediate mode (i.e., don't wait for the command to finish) for some |
623 | commands (e.g., rewind). | |
e40c76c0 MK |
624 | .PP |
625 | An example: | |
088a639b | 626 | .in +4n |
fea681da | 627 | .nf |
e40c76c0 MK |
628 | |
629 | struct mtop mt_cmd; | |
630 | mt_cmd.mt_op = MTSETDRVBUFFER; | |
631 | mt_cmd.mt_count = MT_ST_BOOLEANS | | |
632 | MT_ST_BUFFER_WRITES | MT_ST_ASYNC_WRITES; | |
633 | ioctl(fd, MTIOCTOP, mt_cmd); | |
fea681da | 634 | .fi |
e40c76c0 | 635 | .in |
fea681da | 636 | .RE |
fea681da MK |
637 | .IP "" |
638 | The default block size for a device can be set with | |
e40c76c0 MK |
639 | .B MT_ST_DEF_BLKSIZE |
640 | and the default density code can be set with | |
641 | .BR MT_ST_DEFDENSITY . | |
c13182ef | 642 | The values for the parameters are or'ed |
fea681da MK |
643 | with the operation code. |
644 | .IP "" | |
645 | With kernels 2.1.x and later, the timeout values can be set with the | |
e40c76c0 MK |
646 | subcommand |
647 | .B MT_ST_SET_TIMEOUT | |
648 | ORed with the timeout in seconds. | |
fea681da MK |
649 | The long timeout (used for rewinds and other commands |
650 | that may take a long time) can be set with | |
e40c76c0 | 651 | .BR MT_ST_SET_LONG_TIMEOUT . |
c13182ef | 652 | The kernel defaults are very long to |
fea681da | 653 | make sure that a successful command is not timed out with any |
c13182ef MK |
654 | drive. |
655 | Because of this the driver may seem stuck even if it is only | |
656 | waiting for the timeout. | |
657 | These commands can be used to set more | |
658 | practical values for a specific drive. | |
659 | The timeouts set for one device | |
fea681da | 660 | apply for all devices linked to the same drive. |
e2af0daf MK |
661 | .IP "" |
662 | Starting from kernels 2.4.19 and 2.5.43, the driver supports a status | |
663 | bit which indicates whether the drive requests cleaning. | |
664 | The method used by the | |
665 | drive to return cleaning information is set using the | |
e40c76c0 MK |
666 | .B MT_ST_SEL_CLN |
667 | subcommand. | |
c13182ef MK |
668 | If the value is zero, the cleaning |
669 | bit is always zero. | |
670 | If the value is one, the TapeAlert data defined | |
671 | in the SCSI-3 standard is used (not yet implemented). | |
672 | Values 2-17 are | |
673 | reserved. | |
674 | If the lowest eight bits are >= 18, bits from the extended | |
675 | sense data are used. | |
676 | The bits 9-16 specify a mask to select the bits | |
e2af0daf MK |
677 | to look at and the bits 17-23 specify the bit pattern to look for. |
678 | If the bit pattern is zero, one or more bits under the mask indicate | |
c13182ef | 679 | the cleaning request. |
c7094399 | 680 | If the pattern is nonzero, the pattern must match |
e2af0daf | 681 | the masked sense data byte. |
73d8cece | 682 | .SS MTIOCGET \(em get status |
fea681da MK |
683 | .PP |
684 | This request takes an argument of type | |
8478ee02 | 685 | .IR "(struct mtget *)" . |
fea681da | 686 | .PP |
088a639b | 687 | .in +4n |
fea681da | 688 | .nf |
e40c76c0 | 689 | /* structure for MTIOCGET \- mag tape get status command */ |
fea681da | 690 | struct mtget { |
cf0a9ace MK |
691 | long mt_type; |
692 | long mt_resid; | |
e2af0daf | 693 | /* the following registers are device dependent */ |
cf0a9ace MK |
694 | long mt_dsreg; |
695 | long mt_gstat; | |
696 | long mt_erreg; | |
e2af0daf | 697 | /* The next two fields are not always used */ |
cf0a9ace MK |
698 | daddr_t mt_fileno; |
699 | daddr_t mt_blkno; | |
fea681da MK |
700 | }; |
701 | .fi | |
e40c76c0 | 702 | .in |
f19a0f03 | 703 | .IP \fImt_type\fP 11 |
fea681da | 704 | The header file defines many values for |
f19a0f03 | 705 | .IR mt_type , |
fea681da | 706 | but the current driver reports only the generic types |
e40c76c0 MK |
707 | .B MT_ISSCSI1 |
708 | (Generic SCSI-1 tape) | |
709 | and | |
710 | .B MT_ISSCSI2 | |
711 | (Generic SCSI-2 tape). | |
f19a0f03 | 712 | .IP \fImt_resid\fP |
fea681da | 713 | contains the current tape partition number. |
f19a0f03 | 714 | .IP \fImt_dsreg\fP |
fea681da MK |
715 | reports the drive's current settings for block size (in the low 24 |
716 | bits) and density (in the high 8 bits). | |
e40c76c0 | 717 | These fields are defined by |
979c2c91 | 718 | .BR MT_ST_BLKSIZE_SHIFT , |
e40c76c0 MK |
719 | .BR MT_ST_BLKSIZE_MASK , |
720 | .BR MT_ST_DENSITY_SHIFT , | |
721 | and | |
722 | .BR MT_ST_DENSITY_MASK . | |
f19a0f03 | 723 | .IP \fImt_gstat\fP |
fea681da MK |
724 | reports generic (device independent) status information. |
725 | The header file defines macros for testing these status bits: | |
726 | .RS | |
727 | .HP 4 | |
e40c76c0 | 728 | \fBGMT_EOF\fP(\fIx\fP): |
fea681da | 729 | The tape is positioned just after a filemark |
979c2c91 | 730 | (always false after an |
e40c76c0 MK |
731 | .B MTSEEK |
732 | operation). | |
fea681da | 733 | .HP |
e40c76c0 | 734 | \fBGMT_BOT\fP(\fIx\fP): |
fea681da | 735 | The tape is positioned at the beginning of the first file (always false |
e40c76c0 MK |
736 | after an |
737 | .B MTSEEK | |
738 | operation). | |
fea681da | 739 | .HP |
e40c76c0 | 740 | \fBGMT_EOT\fP(\fIx\fP): |
fea681da MK |
741 | A tape operation has reached the physical End Of Tape. |
742 | .HP | |
e40c76c0 | 743 | \fBGMT_SM\fP(\fIx\fP): |
fea681da | 744 | The tape is currently positioned at a setmark |
e40c76c0 MK |
745 | (always false after an |
746 | .B MTSEEK | |
747 | operation). | |
fea681da | 748 | .HP |
e40c76c0 | 749 | \fBGMT_EOD\fP(\fIx\fP): |
fea681da MK |
750 | The tape is positioned at the end of recorded data. |
751 | .HP | |
e40c76c0 | 752 | \fBGMT_WR_PROT\fP(\fIx\fP): |
fea681da MK |
753 | The drive is write-protected. |
754 | For some drives this can also mean that the drive does not support | |
755 | writing on the current medium type. | |
756 | .HP | |
e40c76c0 | 757 | \fBGMT_ONLINE\fP(\fIx\fP): |
fea681da | 758 | The last |
5e21af3a | 759 | .BR open (2) |
fea681da MK |
760 | found the drive with a tape in place and ready for operation. |
761 | .HP | |
e40c76c0 | 762 | \fBGMT_D_6250\fP(\fIx\fP), \fBGMT_D_1600\fP(\fIx\fP), \fBGMT_D_800\fP(\fIx\fP): |
fea681da MK |
763 | This \(lqgeneric\(rq status information reports the current |
764 | density setting for 9-track \(12" tape drives only. | |
765 | .HP | |
e40c76c0 | 766 | \fBGMT_DR_OPEN\fP(\fIx\fP): |
fea681da MK |
767 | The drive does not have a tape in place. |
768 | .HP | |
e40c76c0 | 769 | \fBGMT_IM_REP_EN\fP(\fIx\fP): |
c13182ef MK |
770 | Immediate report mode. |
771 | This bit is set if there are no guarantees that | |
fea681da | 772 | the data has been physically written to the tape when the write call |
c13182ef MK |
773 | returns. |
774 | It is set zero only when the driver does not buffer data and | |
fea681da | 775 | the drive is set not to buffer data. |
e2af0daf | 776 | .HP |
e40c76c0 | 777 | \fBGMT_CLN\fP(\fIx\fP): |
c13182ef | 778 | The drive has requested cleaning. |
74aace8a | 779 | Implemented in kernels since 2.4.19 and 2.5.43. |
fea681da | 780 | .RE |
f19a0f03 | 781 | .IP \fImt_erreg\fP |
fea681da | 782 | The only field defined in |
f19a0f03 | 783 | .I mt_erreg |
fea681da | 784 | is the recovered error count in the low 16 bits (as defined by |
e40c76c0 MK |
785 | .BR MT_ST_SOFTERR_SHIFT |
786 | and | |
787 | .BR MT_ST_SOFTERR_MASK . | |
fea681da MK |
788 | Due to inconsistencies in the way drives report recovered errors, this |
789 | count is often not maintained (most drives do not by default report | |
790 | soft errors but this can be changed with a SCSI MODE SELECT command). | |
f19a0f03 | 791 | .IP \fImt_fileno\fP |
fea681da MK |
792 | reports the current file number (zero-based). |
793 | This value is set to \-1 when the file number is unknown (e.g., after | |
e40c76c0 MK |
794 | .BR MTBSS |
795 | or | |
796 | .BR MTSEEK ). | |
f19a0f03 | 797 | .IP \fImt_blkno\fP |
fea681da MK |
798 | reports the block number (zero-based) within the current file. |
799 | This value is set to \-1 when the block number is unknown (e.g., after | |
e40c76c0 MK |
800 | .BR MTBSF , |
801 | .BR MTBSS , | |
802 | or | |
803 | .BR MTSEEK ). | |
73d8cece | 804 | .SS MTIOCPOS \(em get tape position |
fea681da MK |
805 | .PP |
806 | This request takes an argument of type | |
8478ee02 | 807 | .I "(struct mtpos *)" |
fea681da MK |
808 | and reports the drive's notion of the current tape block number, |
809 | which is not the same as | |
f19a0f03 | 810 | .I mt_blkno |
e40c76c0 MK |
811 | returned by |
812 | .BR MTIOCGET . | |
979c2c91 | 813 | This drive must be a SCSI-2 drive that supports the |
e40c76c0 | 814 | .B "READ POSITION" |
fea681da MK |
815 | command (device-specific address) |
816 | or a Tandberg-compatible SCSI-1 drive (Tandberg, Archive | |
817 | Viper, Wangtek, ... ). | |
818 | .PP | |
088a639b | 819 | .in +4n |
fea681da | 820 | .nf |
e40c76c0 | 821 | /* structure for MTIOCPOS \- mag tape get position command */ |
cf0a9ace MK |
822 | struct mtpos { |
823 | long mt_blkno; /* current block number */ | |
fea681da | 824 | }; |
fea681da | 825 | .fi |
e40c76c0 | 826 | .in |
47297adb | 827 | .SH RETURN VALUE |
e40c76c0 MK |
828 | .TP 14 |
829 | .TP | |
830 | .B EACCES | |
fea681da MK |
831 | An attempt was made to write or erase a write-protected tape. |
832 | (This error is not detected during | |
5e21af3a | 833 | .BR open (2).) |
e40c76c0 MK |
834 | .TP |
835 | .B EBUSY | |
fea681da MK |
836 | The device is already in use or the driver was unable to allocate a |
837 | buffer. | |
e40c76c0 MK |
838 | .TP |
839 | .B EFAULT | |
840 | The command parameters point to memory not belonging to the calling | |
841 | process. | |
842 | .TP | |
843 | .B EINVAL | |
fea681da | 844 | An |
5e21af3a | 845 | .BR ioctl (2) |
e935e108 | 846 | had an invalid argument, or a requested block size was invalid. |
e40c76c0 MK |
847 | .TP |
848 | .B EIO | |
849 | The requested operation could not be completed. | |
850 | .TP | |
851 | .B ENOMEM | |
852 | The byte count in | |
853 | .BR read (2) | |
854 | is smaller than the next physical block on the tape. | |
855 | (Before 2.2.18 and 2.4.0-test6 the extra bytes have been | |
856 | silently ignored.) | |
857 | .TP | |
858 | .B ENOSPC | |
859 | A write operation could not be completed because the tape reached | |
860 | end-of-medium. | |
861 | .TP | |
862 | .B ENOSYS | |
fea681da | 863 | Unknown |
5e21af3a | 864 | .BR ioctl (2). |
e40c76c0 MK |
865 | .TP |
866 | .B ENXIO | |
867 | During opening, the tape device does not exist. | |
868 | .TP | |
869 | .B EOVERFLOW | |
870 | An attempt was made to read or write a variable-length block that is | |
871 | larger than the driver's internal buffer. | |
872 | .TP | |
873 | .B EROFS | |
874 | Open is attempted with | |
875 | .B O_WRONLY | |
876 | or | |
877 | .B O_RDWR | |
878 | when the tape in the drive is write-protected. | |
fea681da | 879 | .SH FILES |
cba04495 MK |
880 | .TP 12 |
881 | .I /dev/st* | |
882 | the auto-rewind SCSI tape devices | |
883 | .TP 12 | |
884 | .I /dev/nst* | |
24b74457 | 885 | the nonrewind SCSI tape devices |
d2dc6294 MK |
886 | .\" .SH AUTHOR |
887 | .\" The driver has been written by Kai M\(:akisara (Kai.Makisara@metla.fi) | |
888 | .\" starting from a driver written by Dwayne Forsyth. | |
889 | .\" Several other | |
890 | .\" people have also contributed to the driver. | |
fea681da | 891 | .SH NOTES |
e40c76c0 MK |
892 | .IP 1. 4 |
893 | When exchanging data between systems, both systems have to agree on | |
c13182ef MK |
894 | the physical tape block size. |
895 | The parameters of a drive after startup | |
fea681da | 896 | are often not the ones most operating systems use with these |
c13182ef MK |
897 | devices. |
898 | Most systems use drives in variable-block mode if the drive | |
899 | supports that mode. | |
900 | This applies to most modern drives, including | |
901 | DATs, 8mm helical scan drives, DLTs, etc. | |
902 | It may be advisable to use | |
e40c76c0 MK |
903 | these drives in variable-block mode also in Linux (i.e., use |
904 | .B MTSETBLK | |
905 | or | |
906 | .B MTSETDEFBLK | |
907 | at system startup to set the mode), at least when | |
c13182ef MK |
908 | exchanging data with a foreign system. |
909 | The drawback of | |
fea681da MK |
910 | this is that a fairly large tape block size has to be used to get |
911 | acceptable data transfer rates on the SCSI bus. | |
e40c76c0 MK |
912 | .IP 2. |
913 | Many programs (e.g., | |
914 | .BR tar (1)) | |
915 | allow the user to specify the blocking | |
c13182ef MK |
916 | factor on the command line. |
917 | Note that this determines the physical block | |
e2af0daf | 918 | size on tape only in variable-block mode. |
e40c76c0 MK |
919 | .IP 3. |
920 | In order to use SCSI tape drives, the basic SCSI driver, | |
fea681da | 921 | a SCSI-adapter driver and the SCSI tape driver must be either |
c13182ef MK |
922 | configured into the kernel or loaded as modules. |
923 | If the SCSI-tape | |
fea681da MK |
924 | driver is not present, the drive is recognized but the tape support |
925 | described in this page is not available. | |
e40c76c0 MK |
926 | .IP 4. |
927 | The driver writes error messages to the console/log. | |
c13182ef | 928 | The SENSE |
fea681da MK |
929 | codes written into some messages are automatically translated to text |
930 | if verbose SCSI messages are enabled in kernel configuration. | |
e40c76c0 MK |
931 | .IP 5. |
932 | The driver's internal buffering allows good throughput in fixed-block | |
c13182ef | 933 | mode also with small |
5e21af3a | 934 | .BR read (2) |
c13182ef | 935 | and |
5e21af3a | 936 | .BR write (2) |
c13182ef MK |
937 | byte counts. |
938 | With direct transfers | |
e2af0daf MK |
939 | this is not possible and may cause a surprise when moving to the 2.6 |
940 | kernel. | |
941 | The solution is to tell the software to use larger transfers (often | |
942 | telling it to use larger blocks). | |
943 | If this is not possible, direct transfers can be disabled. | |
2b2581ee | 944 | .\" .SH COPYRIGHT |
e37e3282 MK |
945 | .\" Copyright \(co 1995 Robert K. Nichols. |
946 | .\" .br | |
947 | .\" Copyright \(co 1999-2005 Kai M\(:akisara. | |
948 | .\" .PP | |
4b72fb64 | 949 | .\" %%%LICENSE_START(verbatim) |
e37e3282 MK |
950 | .\" Permission is granted to make and distribute verbatim copies of this |
951 | .\" manual provided the copyright notice and this permission notice are | |
952 | .\" preserved on all copies. | |
953 | .\" Additional permissions are contained in the header of the source file. | |
47297adb | 954 | .SH SEE ALSO |
e37e3282 | 955 | .BR mt (1) |
fea681da | 956 | .PP |
cba04495 MK |
957 | The file |
958 | .I drivers/scsi/README.st | |
959 | or | |
960 | .I Documentation/scsi/st.txt | |
173fe7e7 | 961 | (kernel >= 2.6) in the Linux kernel source tree contains |
e37e3282 | 962 | the most recent information about the driver and its configuration |
173fe7e7 | 963 | possibilities |