AIX 5L Problem Determination - IBM Redbooks

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lv02 jfs 2 2 1 open/syncd /u/testfs # rmfs /u/testfs rmfs: 0506-921 /u/testfs is currently mounted. # umount /u/testfs # rmfs /u/testfs rmlv: Logical volume lv02 is removed. # lsvg -l testvg testvg: LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT loglv00 jfslog 1 1 1 closed/syncd N/A This example shows how the file system testfs is removed. The first attempt fails because the file system is still mounted. The associated logical volume lv02 is also removed. The jfslog remains defined on the volume group. 7.4.7 Different output from du and df commands Sometimes du and df commands are used to get a free block value. df is used to report the total block count, and then the value returned by du -s /filesystem_name is subtracted from that total to calculate the free block value. However, this method of calculation yields a value that is greater than the free block value reported by df. At AIX Version 4.1 and later, both df and du default to 512-byte units. Sample output from the du and df commands is below: # du -s /tmp 152 /tmp # df /tmp Filesystem 512-blocks Free %Used Iused %Iused Mounted on /dev/hd3 24576 23320 6% 33 1% /tmp Here (total from df) - (used from du) + (false free block count): 24576 - 152 = 24424. 24424 is greater than 23320. The reason for this discrepancy involves the implementation of du and df. du -s traverses the file tree, adding up the number of blocks allocated to each directory, symlink, and file as reported by the stat() system call. This is how du arrives at its total value. df looks at the file system disk block allocation maps to arrive at its total and free values. 7.4.8 Enhanced journaled file system The enhanced journaled file system (JFS2) contains several architectural differences over the standard JFS, including: ► Variable number of i-nodes for enhanced journaled file system JFS2 allocates i-nodes as needed. Therefore, the number of i-nodes available is limited by the size of the file system itself. 156 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques
► Specifying file system block size File system block size is specified during the file system's creation with the crfs and mkfs commands or by using the SMIT. The decision of file system block size should be based on the projected size of files contained by the file system. ► Identifying file system block size The file system block size value can be identified with the lsfs command or the System Management Interface Tool (SMIT). For application programs, the statfs subroutine can be used to identify the file system block size. ► Compatibility and migration The enhanced journaled file system (JFS2) is a new file system and is not compatible with AIX Version 4. ► Device driver limitations A device driver must provide disk block addressability that is the same or smaller than the file system block size. ► Performance costs Although file systems that use block sizes smaller than 4096 bytes as their allocation unit might require substantially less disk space than those using the default allocation unit of 4096 bytes, the use of smaller block sizes can incur performance degradation. ► Increased allocation activity Because disk space is allocated in smaller units for a file system with a block size other than 4096 bytes, allocation activity can occur more often when files or directories are repeatedly extended in size. For example, a write operation that extends the size of a zero-length file by 512 bytes results in the allocation of one block to the file, assuming a block size of 512 bytes. If the file size is extended further by another write of 512 bytes, an additional block must be allocated to the file. Applying this example to a file system with 4096-byte blocks, disk space allocation occurs only once, as part of the first write operation. No additional allocation activity is performed as part of the second write operation since the initial 4096-byte block allocation is large enough to hold the data added by the second write operation. ► Increased block allocation map size More virtual memory and file system disk space might be required to hold block allocation maps for file systems with a block size smaller than 4096 bytes. Blocks serve as the basic unit of disk space allocation, and the allocation state of each block within a file system is recorded in the file system block allocation map. Chapter 7. LVM, file system, and disk problem determination 157
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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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Figure 5-4 Case study Which of the
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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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