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These are the user uploaded subtitles that are being translated: 1 00:00:01,390 --> 00:00:03,280 In this lesson, we're going to be discussing 2 00:00:03,280 --> 00:00:06,400 what is perhaps the most important task of an Oracle 3 00:00:06,400 --> 00:00:09,460 DBA, and that's backup and recovery. 4 00:00:09,460 --> 00:00:12,340 No matter what else happens with your database in terms 5 00:00:12,340 --> 00:00:15,310 of performance problems or data errors, 6 00:00:15,310 --> 00:00:20,290 if you can't recover the loss of media, of data files, 7 00:00:20,290 --> 00:00:23,250 table spaces, the loss of a database, then 8 00:00:23,250 --> 00:00:25,330 you're going to be in trouble really, really soon. 9 00:00:25,330 --> 00:00:27,730 And this is the kind of thing that a DBA 10 00:00:27,730 --> 00:00:30,700 must master and really must practice in order 11 00:00:30,700 --> 00:00:33,170 to get proficient at it. 12 00:00:33,170 --> 00:00:35,460 So when we talk about backup and recovery, 13 00:00:35,460 --> 00:00:37,270 we're really talking about the ability 14 00:00:37,270 --> 00:00:40,280 to recover from a media failure. 15 00:00:40,280 --> 00:00:43,480 So what kinds of things constitute a media failure? 16 00:00:43,480 --> 00:00:45,160 Well, a media failure would be something 17 00:00:45,160 --> 00:00:47,230 like the loss of a disk drive. 18 00:00:47,230 --> 00:00:50,050 So we have a database that's on the D drive 19 00:00:50,050 --> 00:00:54,730 and that drive is lost, or it's on a D drive that's actually 20 00:00:54,730 --> 00:00:58,030 a RAID group of many different disks and maybe more than one 21 00:00:58,030 --> 00:00:59,650 of those is lost. 22 00:00:59,650 --> 00:01:03,170 So those types of things constitute a media failure. 23 00:01:03,170 --> 00:01:05,920 Another thing that would be considered a media failure 24 00:01:05,920 --> 00:01:09,170 would be the loss of a data file. 25 00:01:09,170 --> 00:01:10,900 So someone goes out to the database 26 00:01:10,900 --> 00:01:14,990 and actually deletes a data file accidentally. 27 00:01:14,990 --> 00:01:16,360 Any of those kind of things would 28 00:01:16,360 --> 00:01:19,300 require the intervention of the DBA 29 00:01:19,300 --> 00:01:21,940 in the form of a recovery operation. 30 00:01:21,940 --> 00:01:23,920 So when we talk about backup and recovery, 31 00:01:23,920 --> 00:01:27,160 it's important to remember that what saves us 32 00:01:27,160 --> 00:01:31,420 in situations like a media failure isn't just our backup, 33 00:01:31,420 --> 00:01:34,510 but it's really the entire Oracle recoverability 34 00:01:34,510 --> 00:01:35,710 architecture. 35 00:01:35,710 --> 00:01:39,760 The idea that Oracle is built from the ground up 36 00:01:39,760 --> 00:01:43,630 to be recoverable up to the last committed transaction. 37 00:01:43,630 --> 00:01:46,420 So it rolls into things like redo 38 00:01:46,420 --> 00:01:49,990 logs that record every change in the database, things 39 00:01:49,990 --> 00:01:52,720 like archive logs that can store our reading 40 00:01:52,720 --> 00:01:54,250 logs as they switch. 41 00:01:54,250 --> 00:01:58,630 All of those things go into the concept of backup and recovery. 42 00:01:58,630 --> 00:02:01,450 When we perform backup and recovery operations in Oracle, 43 00:02:01,450 --> 00:02:04,300 we use a tool called Recovery Manager 44 00:02:04,300 --> 00:02:07,300 and RMAN is going to be a command line tool, for the most 45 00:02:07,300 --> 00:02:07,960 part. 46 00:02:07,960 --> 00:02:11,830 It interfaces with other GUI tools, like Enterprise Manager. 47 00:02:11,830 --> 00:02:15,670 But for our purposes, we use it in the command line setting. 48 00:02:15,670 --> 00:02:17,770 It has a number of benefits to it 49 00:02:17,770 --> 00:02:20,080 and probably most importantly, RMAN 50 00:02:20,080 --> 00:02:23,800 performs what's called true block level backups. 51 00:02:23,800 --> 00:02:26,260 So when we think of the idea of doing a backup, 52 00:02:26,260 --> 00:02:28,930 it might be as simple as shutting down the database, 53 00:02:28,930 --> 00:02:31,370 copying all the data files somewhere else. 54 00:02:31,370 --> 00:02:34,630 But if those data files are all half full, 55 00:02:34,630 --> 00:02:36,640 let's say, then we've taken longer 56 00:02:36,640 --> 00:02:39,370 to copy those files than we really needed to. 57 00:02:39,370 --> 00:02:42,700 RMAN is capable, since it's built into the Oracle engine, 58 00:02:42,700 --> 00:02:46,930 of looking at and reading those database blocks in the data 59 00:02:46,930 --> 00:02:48,310 files themselves. 60 00:02:48,310 --> 00:02:52,690 Those are what gets read and written out to backup files. 61 00:02:52,690 --> 00:02:57,250 RMAN is also capable of ignoring empty data file blocks. 62 00:02:57,250 --> 00:03:00,790 So in tablespaces that maybe are only a half full or a quarter 63 00:03:00,790 --> 00:03:06,040 full, it's not required of RMAN to backup those empty blocks. 64 00:03:06,040 --> 00:03:09,580 So that makes our backups faster and higher performing. 65 00:03:09,580 --> 00:03:11,870 RMAN also supports compressed backup. 66 00:03:11,870 --> 00:03:14,980 So the ability to compress our backup on the fly, 67 00:03:14,980 --> 00:03:18,520 further reducing our space requirements for backups. 68 00:03:18,520 --> 00:03:21,100 And also supports encrypted backups, 69 00:03:21,100 --> 00:03:24,530 backups that are built with an encryption key or a password, 70 00:03:24,530 --> 00:03:25,900 something of that nature in order 71 00:03:25,900 --> 00:03:29,440 to make database backups more secure. 72 00:03:29,440 --> 00:03:32,500 Another concept in Oracle's backup and recovery 73 00:03:32,500 --> 00:03:35,150 is something called the fast recovery area 74 00:03:35,150 --> 00:03:37,600 and that's going to be a specialized directory structure 75 00:03:37,600 --> 00:03:40,090 for backup related files. 76 00:03:40,090 --> 00:03:44,280 It's defined by two parameters, db_recovery_file_dest, 77 00:03:44,280 --> 00:03:48,940 the dest being for destination, and db_recovery_file_dest_size. 78 00:03:48,940 --> 00:03:51,340 So the recovery file dest is going 79 00:03:51,340 --> 00:03:53,740 to be a directory that's specified 80 00:03:53,740 --> 00:03:56,890 that will contain all of the backup files, 81 00:03:56,890 --> 00:03:59,680 archive logs, flashback logs, any 82 00:03:59,680 --> 00:04:02,950 of the types of files that are related to backup and recovery. 83 00:04:02,950 --> 00:04:05,410 And Oracle put this in place because there was too 84 00:04:05,410 --> 00:04:09,670 many instances in the real world of DBAs who would do backups 85 00:04:09,670 --> 00:04:13,060 but then would kind of lose track of where everything was. 86 00:04:13,060 --> 00:04:14,980 Because when you do a recovery, a lot of times 87 00:04:14,980 --> 00:04:16,330 you need everything. 88 00:04:16,330 --> 00:04:19,750 You need to make sure you have all of the pieces that comprise 89 00:04:19,750 --> 00:04:23,080 the backup, and there were too many situations where databases 90 00:04:23,080 --> 00:04:25,030 became unrecoverable because there 91 00:04:25,030 --> 00:04:29,900 wasn't any continuity to how DBAs stored their backup files. 92 00:04:29,900 --> 00:04:32,350 So this is a really useful thing to use. 93 00:04:32,350 --> 00:04:34,240 The fast recovery area was formerly 94 00:04:34,240 --> 00:04:37,910 known as the flash recovery area in previous versions. 95 00:04:37,910 --> 00:04:42,140 And so to take a look at what a fast recovery area looks like, 96 00:04:42,140 --> 00:04:45,820 notice that we're in the Oracle based directory on my machine 97 00:04:45,820 --> 00:04:48,460 and there's a directory called fast recovery area. 98 00:04:48,460 --> 00:04:51,070 If we click that, we have the name of the database. 99 00:04:51,070 --> 00:04:52,620 If we have more than one database, 100 00:04:52,620 --> 00:04:53,950 there'll be a list of them here. 101 00:04:53,950 --> 00:04:57,280 Click that and notice the kind of files that are stored here. 102 00:04:57,280 --> 00:05:01,270 So we have archive log files and we have a directory here 103 00:05:01,270 --> 00:05:04,750 that is given the date so we know exactly where our archive 104 00:05:04,750 --> 00:05:06,680 logs are. 105 00:05:06,680 --> 00:05:10,070 We have a control file directory that'll store usually 106 00:05:10,070 --> 00:05:12,180 a copy of the control file. 107 00:05:12,180 --> 00:05:14,200 In this case, we have online logs, 108 00:05:14,200 --> 00:05:16,970 but these are going to be redo logs here in this case. 109 00:05:16,970 --> 00:05:19,920 So all of the recovery related files. 110 00:05:19,920 --> 00:05:22,640 Notice that we don't see here backup related 111 00:05:22,640 --> 00:05:25,820 files because we haven't done any backups on this machine 112 00:05:25,820 --> 00:05:26,480 yet. 113 00:05:26,480 --> 00:05:29,040 Another concept involved in backup and recovery, 114 00:05:29,040 --> 00:05:31,770 at least as it pertains to RMAN, is the repository. 115 00:05:31,770 --> 00:05:33,380 So the repository is a collection 116 00:05:33,380 --> 00:05:35,630 of information about backups. 117 00:05:35,630 --> 00:05:38,270 So you can do all the backups that you want 118 00:05:38,270 --> 00:05:42,350 but what unit remembers all of that information? 119 00:05:42,350 --> 00:05:44,360 What remembers what was backed up 120 00:05:44,360 --> 00:05:46,760 and where it was written to and so on and so forth 121 00:05:46,760 --> 00:05:48,000 for the purposes of recovery? 122 00:05:48,000 --> 00:05:50,600 What was the repository that does that? 123 00:05:50,600 --> 00:05:53,210 And the repository can be two different entities. 124 00:05:53,210 --> 00:05:57,420 First of all, the control file keeps this info by default. 125 00:05:57,420 --> 00:05:59,030 So backup and recovery information 126 00:05:59,030 --> 00:06:00,560 is stored in the control file. 127 00:06:00,560 --> 00:06:01,940 But we could also have it-- 128 00:06:01,940 --> 00:06:04,580 for higher stability and security, 129 00:06:04,580 --> 00:06:07,550 we could have it in a recovery catalog, which is actually 130 00:06:07,550 --> 00:06:10,760 a separate database that we would create where we could 131 00:06:10,760 --> 00:06:14,240 connect to that database and then connect to the database 132 00:06:14,240 --> 00:06:18,110 that we're backing up, and RMAN would talk to both areas 133 00:06:18,110 --> 00:06:21,270 and the recovery catalog would keep that information. 134 00:06:21,270 --> 00:06:24,440 So in the event of a complete loss including the control 135 00:06:24,440 --> 00:06:28,290 file, we would still be able to recover the database. 136 00:06:28,290 --> 00:06:31,890 And finally, archive log versus no archive log mode. 137 00:06:31,890 --> 00:06:34,920 So when we're talking about no archive log mode, 138 00:06:34,920 --> 00:06:38,940 we're talking about that when changes in the database switch, 139 00:06:38,940 --> 00:06:41,670 they're not written out to a static file. 140 00:06:41,670 --> 00:06:44,550 So in no archive log mode, we have the capability 141 00:06:44,550 --> 00:06:47,220 of writing over changes that have occurred 142 00:06:47,220 --> 00:06:49,540 and that makes us non-recoverable. 143 00:06:49,540 --> 00:06:52,560 So when we're running with no archive log mode, 144 00:06:52,560 --> 00:06:55,080 our recovery options are very, very limited 145 00:06:55,080 --> 00:06:56,850 and that must be stressed. 146 00:06:56,850 --> 00:07:01,140 Really, in no archive log mode, about the only thing you can do 147 00:07:01,140 --> 00:07:05,650 is restore your backup and that's as far as you can go. 148 00:07:05,650 --> 00:07:09,720 So if you backup on a Sunday night and you lose media, 149 00:07:09,720 --> 00:07:12,660 data file, or whatever on Thursday, 150 00:07:12,660 --> 00:07:16,800 then you lose all the changes between Sunday and Thursday. 151 00:07:16,800 --> 00:07:19,410 So that's really important to stress. 152 00:07:19,410 --> 00:07:21,720 However, with archive log mode, we 153 00:07:21,720 --> 00:07:24,510 don't have that problem because every change 154 00:07:24,510 --> 00:07:26,430 is stored in static files. 155 00:07:26,430 --> 00:07:28,470 So changes are written to the redo logs, 156 00:07:28,470 --> 00:07:31,540 and then the redo logs are written to archive logs. 157 00:07:31,540 --> 00:07:34,410 So the use of archive log mode allows us 158 00:07:34,410 --> 00:07:36,700 to do things like hot backups. 159 00:07:36,700 --> 00:07:38,820 So backups while the database is up. 160 00:07:38,820 --> 00:07:42,330 We can do a recovery up until the very point of failure. 161 00:07:42,330 --> 00:07:45,060 The very last committed transaction 162 00:07:45,060 --> 00:07:47,910 can be recovered when we're in archive log mode. 163 00:07:47,910 --> 00:07:50,850 And we can also do things like time-based recoveries. 164 00:07:50,850 --> 00:07:54,940 So we can recover a database to the point in the past. 165 00:07:54,940 --> 00:07:59,760 So how do we decide if we're an archive log mode or no archive 166 00:07:59,760 --> 00:08:01,080 log mode? 167 00:08:01,080 --> 00:08:04,490 Let's go into our database, Assist DBA, 168 00:08:04,490 --> 00:08:09,270 and we'll execute a command called archive log list. 169 00:08:09,270 --> 00:08:12,300 So archive log list tells us that our database log 170 00:08:12,300 --> 00:08:14,580 mode is no archive mode. 171 00:08:14,580 --> 00:08:18,720 Automatic archival is disabled, and our archive destination, 172 00:08:18,720 --> 00:08:23,250 should we enable archive log, is a keyword use DB recovery file 173 00:08:23,250 --> 00:08:27,060 desk, which means it is writing to the fast recovery area. 174 00:08:27,060 --> 00:08:28,890 So our database is open right now. 175 00:08:28,890 --> 00:08:31,940 How can we put our database in archive log mode 176 00:08:31,940 --> 00:08:34,980 so we can have the most recoverability options? 177 00:08:34,980 --> 00:08:38,490 Well, in order to enable archive log mode, it's very simple 178 00:08:38,490 --> 00:08:40,680 but we need to be in the mount state. 179 00:08:40,680 --> 00:08:42,390 So we're going to shut down our database. 180 00:08:46,490 --> 00:08:48,710 We're going to start up in mount mode. 181 00:08:51,450 --> 00:08:53,990 So now we're in the mount state, and we simply 182 00:08:53,990 --> 00:08:59,440 type alter database archive log. 183 00:08:59,440 --> 00:09:01,660 Now we're an archive log mode so we 184 00:09:01,660 --> 00:09:05,650 need to start up the database, at least to the open state, 185 00:09:05,650 --> 00:09:06,730 alter database open. 186 00:09:09,260 --> 00:09:12,900 So with our database open, we can do archive log list again 187 00:09:12,900 --> 00:09:14,250 to check. 188 00:09:14,250 --> 00:09:19,490 Now we are in archive mode with automatic archival enabled. 189 00:09:19,490 --> 00:09:22,650 We want to make sure of this and kind of see it for ourselves, 190 00:09:22,650 --> 00:09:27,890 we could do an alter system switch log file. 191 00:09:27,890 --> 00:09:31,240 So this will switch from the one redo log to the next 192 00:09:31,240 --> 00:09:33,870 and write out our archive log. 193 00:09:33,870 --> 00:09:37,130 We go back to our fast recovery area. 194 00:09:37,130 --> 00:09:39,110 We notice there is a new folder written 195 00:09:39,110 --> 00:09:42,710 for the date and an archive log written out. 196 00:09:42,710 --> 00:09:44,870 So now we're in archive log mode and fully 197 00:09:44,870 --> 00:09:48,550 prepared to do backups and recoveries. 16663

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