AIX 5L Problem Determination - IBM Redbooks

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In many cases, restoration of the backup of the superblock to the primary superblock will recover the file system. If this does not resolve the problem, recreate the file system and restore the data from a backup. 7.4.4 Sparse file allocation Some applications, particularly databases, maintain data in sparse files. Files that do not have disk blocks allocated for each logical block are called sparse files. If the file offsets are greater than 4 MB, then a large disk block of 128 KB is allocated. Applications using sparse files larger than 4 MB may require more disk blocks in a file system enabled for large files than in a regular file system. In the case of sparse files, the output of the ls command is not showing the actual file size, but is reporting the number of bytes between the first and last blocks allocated to the file, as shown in the following example: # ls -l /tmp/sparsefile -rw-r--r-- 1 root system 100000000 Jul 16 20:57 /tmp/sparsefile The du command can be used to see the actual allocation, since it reports the blocks actually allocated and in use by the file. Use du -rs to report the number of allocated blocks on disk. # du -rs /tmp/sparsefile 256 /tmp/sparsefile Note: The tar command does not preserve the sparse nature of any file that is sparsely allocated. Any file that was originally sparse before the restoration will have all space allocated within the file system for the size of the file. New AIX 5L options for the backup and restore command are useful for sparse files. Using the dd command in combination with your own backup script will solve this problem. 7.4.5 Unmount problems A file system cannot be unmounted if any references are still active within that file system. The following error message will be displayed: Device busy or A device is already mounted or cannot be unmounted 154 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques
The following situations can leave open references to a mounted file system. ► Files are open within a file system. These files must be closed before the file system can be unmounted. The fuser command is often the best way to determine what is still active in the file system. The fuser command will return the process IDs for all processes that have open references within a specified file system, as shown in the following example: # umount /home umount: 0506-349 Cannot unmount /dev/hd1: The requested resource is busy. # fuser -x -c /home /home: 11630 # ps -fp 11630 UID PID PPID C STIME TTY TIME CMD guest 11630 14992 0 16:44:51 pts/1 0:00 -sh # kill -1 11630 # umount /home The process having an open reference can be killed by using the kill command (sending a SIGHUP), and the unmount can be accomplished. A stronger signal may be required, such as SIGKILL. ► If the file system is still busy and still cannot be unmounted, this could be due to a kernel extension that is loaded but exists within the source file system. The fuser command will not show these kinds of references, since a user process is not involved. However, the genkex command will report on all loaded kernel extensions. ► File systems are still mounted within the file system. Unmount these file systems before the file system can be unmounted. If any file system is mounted within a file system, this leaves open references in the source file system at the mount point of the other file system. Use the mount command to get a list of mounted file systems. Unmount all the file systems that are mounted within the file system to be unmounted. 7.4.6 Removing file systems When removing a JFS, the file system must be unmounted before it can be removed. The command for removing file systems is rmfs. In the case of a JFS, the rmfs command removes both the logical volume on which the file system resides and the associated stanza in the /etc/filesystems file. If the file system is not a JFS, the command removes only the associated stanza in the /etc/filesystems file, as shown in the following example: # lsvg -l testvg testvg: LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT loglv00 jfslog 1 1 1 open/syncd N/A Chapter 7. LVM, file system, and disk problem determination 155
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ibm.com/redbooks IBM Certification
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Note: Before using this information
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3.5.1 The /etc/inittab file . . . .
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7.2.1 Data relocation . . . . . . .
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9.9.1 The lslicense command . . . .
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x IBM ^ Certification Study Guide -
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10-12 Performance tuning flowchart
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8-7 Commonly used flags of the rout
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Trademarks The following terms are
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This publication does not replace p
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Comments welcome Your comments are
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1.1 Certification requirements To a
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e. Verify that file systems are mou
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Preparation for this exam is the to
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2.1 Defining the problem The first
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If the problem occurs on more than
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2.4.1 Answers The following are the
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3.1 A general overview of the boot
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mainly to components on the motherb
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Figure 3-3 Task selection menu in d
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3.2.2 PCI systems next step is to s
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3.3 Boot phase 1 Newer PCI architec
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3.4 Boot phase 2 In boot phase 2, t
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As mentioned, there are a lot of di
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3.4.3 LED 518 product documentation
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Figure 3-9 Boot phase 3 /etc/initta
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3.5.2 LED 553 3.5.3 LED c31 3.5.4 L
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3.5.5 pSeries servers A specific LE
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When the system is gracefully shut
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LED Reason/action c31 Define the co
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3. A file system is being mounted b
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3.9.1 Answers 3.10 Exercises The fo
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4.1 Hardware basics RS/6000 and pSe
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The most important fields in the pr
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Figure 4-1 Main diagnostics menu Th
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► Full testing requires that the
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3. Place the CD-ROM into the drive.
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Note: This service aid is only pres
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2. Select Change Show use of an SSA
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LED 299 A LED code of 299 shows tha
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Figure 4-2 Format of the 103 code m
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4.5 Quiz The following assessment q
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4.5.1 Answers 4.6 Exercises The fol
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5.1 Configuring the dump device Pri
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5.2 Starting a system dump A user-i
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A command status screen will be dis
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If the system does not have a key s
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The shconf command is invoked when
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5.4 Increasing the size of the dump
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Setting output device to /dev/rmt0.
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Look at the time of the dump and th
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Failure Causes SOFTWARE PROGRAM Rec
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Using crash, you can examine: ► A
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► ? or help[] Lists all subcomman
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LR: .waitproc+d4 (0000edc4) 2ff3b38
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DSIRR Data Storage Interrupt Reason
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*prevthread:0xe6000000 *nextthread:
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In this example, the VMM return cod
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The snap command syntax is as follo
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Flag Description -t Format Lists ea
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Flag Description -p Device Temporar
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Figure 5-3 Error log case study 2.
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telnet: connect: A remote host did
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9.2.4 Telnet error If when attempti
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user is limited and defined as an A
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9.4.3 A full file system uid=0(root
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9.5.1 Trace hook IDs The events tra
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your trace, the system may be traci
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113 0.004261661 0.001518 unlock: lo
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If the sendmail command encounters
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9.8 Printing Task SMIT fast path Co
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Action or function System V PowerPC
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Switching between subsystems The op
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Flag Description -s Subsystem Speci
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9.10 Quiz Flag Description -O Optio
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6. A user has the ability to ping t
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232 IBM ^ Certification Study Guide
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Figure 10-1 General performance tun
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Display previously captured data Th
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10.1.2 The vmstat command The vmsta
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later). The method used in AIX Vers
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second. Large values indicate a CPU
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kernel routine records the process
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syncd 1 2 2 0 0 0 sh 1 1 1 0 0 0 sl
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The memory columns The memory colum
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The sr column The sr column shows t
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If you want to sort to the sixth co
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► Workload Management Class (-W)
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schedtune limitations The schedtune
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schedtune parameters are reset by t
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Normal files are automatically mapp
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tty: tin tout avg-cpu: % user % sys
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When looking for performance proble
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those that do not. If you are runni
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The netstat -m command The netstat
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spec buf 1 0 0 0 128 128 0 locking
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Late Collision Errors The Late Coll
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The retrans column displays the num
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Figure 10-3 Web-based System Manage
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Superclasses A superclass is a clas
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► Shared subclass: This subclass
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The sequence of attributes within a
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This manual assignment can be done
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This defines three levels of privil
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The class assignment is done by WLM
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Figure 10-8 shows the SMIT panel wh
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Figure 10-10 SMIT panel for rset re
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10.6.1 The dbx command The dbx comm
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Subcommand Description return Conti
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15) phxent_dd [5 entries] 16) kbddd
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10.8 Command summary The following
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10.8.4 The nfsstat command 10.9 Qui
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6. Which command will show system c
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11.1 Overview 11.1.1 Terminology 11
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Note: Before installing a new set o
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► APAR number, such as IY00301. I
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► To install all filesets associa
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Table 11-2 Commonly used flags of t
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11.5 Quiz Flag Description -f Check
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- A Web server The browser must be
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Figure 12-2 HTTP filesets If you ar
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- Remote computer Type the remote d
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Figure 12-4 Documentation Library S
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CISPR International Special Committ
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I/O Input/Output I 2 C Inter Integr
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OEM Original Equipment Manufacturer
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SPM System Performance Measurement
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Other resources These publications
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phase1 figure 23 phase2 15, 24, 36
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pc.statd 189 daemons shdaemon 73 te
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host name resolution telnet login p
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N name resolution diagnostic 185 pr
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ecent CPU usage 241 recovering an i
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System Resource Controller (SRC) 13
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