2 Commands Listed by Function

This chapter groups the samu commands by task and function. Locate the task that you need to carry out and then see the alphabetical command listings in Chapter 3, "Operator Commands", and Chapter 4, "Service and Support Commands", for more information:

• "Controlling Operator Displays"

• "Tuning I/O Performance"

• "Configuring File Systems"

• "Configuring Shared File Systems"

• "Configuring Single-Writer/Multi-Reader File Systems"

• "Configuring File Systems for Oracle Real Application Clusters (RAC)"

• "Managing Storage Devices"

• "Managing Robotic Storage Libraries"

• "Archiving"

• "Staging"

• "Working with Service and Support Representatives"

Controlling Operator Displays

This section lists the samu operator display commands. Note that each command is a lower-case letter of the alphabet (uppercase letters are described in Chapter 4, "Service and Support Commands".

• a (Display Archiver Status Screen)

• c (Display Device Configuration Screen)

• d (Display Daemon Trace Controls Screen)

• f (Display File Systems Screen)

• h (Display the Help Screen)

• l (Display Utilization Information)

• m (Display the Mass Storage Status Screen)

• n (Display the Staging Status Screen)

• o (Display the Optical Disk Status Screen)

• p (Display the Removable Media Load Requests Screen)

• r (Display the Removable Media Status Screen

• refresh (Set the Automatic Refresh Interval for the samu Display)

• s (Display Device Status Screen)

• snap (Save a Snapshot of the Current Screen to a File)

• t (Display Tape Drive Status Screen)

• u (Display Staging Queue Screen)

• v (Display Robot VSN Catalog Screen)

• w (Display the Pending Stage Queue Screen)

Tuning I/O Performance

This section starts with a brief summary of the factors that affect file-system performance, the objectives of performance tuning, and the Oracle HSM features that support tuning efforts. It then links to the commands that control the input/output methods that Oracle HSM supports: Paged (Buffered) I/O, Direct I/O, and Switched I/O.

Understanding I/O Performance Tuning Objectives and Options

Disk I/O (input/output) involves mechanical processes that are vastly more time-consuming than other file-system operations. So I/O performance tuning focuses on keeping the mechanical work to the absolute minimum necessary for transferring a given amount of data. This means reducing both the number of separate I/Os per data transfer and the number of seeks operations required to service each I/O.

So the basic objectives of I/O tuning are as follows:

• Read and write large blocks of data.

• Write blocks in units that align with the sector boundaries of the underlying media, so that the disk controller does not have to read and modify existing data before writing the new data.

• Queue up small I/Os in cache and write larger, combined I/Os to disk.

To achieve these objectives, Oracle HSM file systems support three kinds of I/O, each of which addresses a different set of file-system usage patterns.

Paged (Buffered) I/O is the default method because it works well with the usage characteristics of common, general-purpose file-systems. Most file-systems are used by multiple users and applications. Each reads and writes small amounts of data in blocks that often depend on application design rather than on disk sector boundaries. File access tends to be random rather than sequential. When properly configured, paged I/O is ideal for this kind of use. User data is cached in virtual memory pages until the Oracle Solaris kernel writes the data to disk. So users and applications write to and read from cache memory, where random access and small block sizes are less of a problem. Performance-critical, physical reads and writes to and from disk are made in larger, better aligned, more nearly sequential chunks.

Direct I/O addresses limitations of paged I/O that become apparent in file systems are dedicated to particular types of data, such as medical imagery, geological information bases, and real-time surveillance imagery. Generally, users and applications read and write large files sequentially in blocks that align with disk sector boundaries. So paging has no performance advantages. It does, however, impose system overhead and delays the point at which data is securely written from memory to disk—the latter potentially critical in realtime applications. In this situation, direct I/O can significantly improve performance. Data is transferred directly between the local buffer on the application host and the Oracle HSM disk device, with no intermediate delays or additional complication.

Switched I/O is a combination of the other two that works by setting an I/O size threshold for the file system. Paged I/O is used until this threshold is reached. Thereafter, the system automatically switches to direct I/O until the request has been completely addressed. Most small requests are handled before the threshold is reached, so they are read from and written to cache memory and transferred to or from disk asynchronously, in larger, better aligned units. But larger requests are handled directly once the threshold is exceeded, without extra caching overhead.

Paged (Buffered) I/O

The following commands let you tune the paged I/O characteristics of Oracle HSM file systems based on file size and usage.

• flush_behind (Set the Flush-Behind Parameter)

• force_nfs_async (Force Asynchronous NFS)

• noforce_nfs_async (Do Not Force Asynchronous NFS)

• readahead (Set The Maximum Read-Ahead Parameter)

• wr_throttle (Set the Maximum Size of Outstanding Writes)

• writebehind (Set the Write-Behind Parameter)

Direct I/O

The following samu commands let you change the default I/O behavior of a specified family set device from paged I/O to direct I/O and vice versa:

• forcedirectio (Use Direct I/O by Default)

• noforcedirectio (Do Not Use Direct I/O by Default)

The commands below control how sparse files are initialized during direct I/O:

• dio_szero (Zero Uninitialized Areas of Sparse Files During Direct I/O)

• nodio_szero (Do Not Zero Uninitialized Areas of Sparse Files with Direct I/O)

Switched I/O

As described above, Oracle HSM can be configured to switch from paged I/O to direct I/O when file reads and/or writes exceed specified thresholds. The commands below enable this feature and define the thresholds:

• dio_rd_consec (Limit the Number of Consecutive Direct Reads)

• dio_rd_form_min (Set the Size of Well-Aligned Direct I/O Reads)

• dio_rd_ill_min (Set the Size of Misaligned Direct I/O Reads)

• dio_wr_consec (Limit the Number of Consecutive Direct Writes)

• dio_wr_form_min (Set the Size of Well-Formed Direct I/O Writes)

• dio_wr_ill_min (Set the Size of Misaligned Direct I/O Writes)

Configuring File Systems

• add (Add Equipment to a Mounted File System)

• atime (Configure Access Time Updates for a File System)

• def_retention (Set Default WORM Retention Time)

• mm_stripe (Set the Metadata Stripe Width)

• noatime (Disable Access Time Updates for a File System)

• noqwrite (Disable Simultaneous Reads/Writes from Different Threads)

• nosuid (Mount a File System with setuid Execution Disabled)

• nosw_raid (Turn Off Software RAID Mode)

• notrace (Disable File System Tracing)

• qwrite (Enable Simultaneous Reads/Writes to a File from Different Threads)

• remove (Move Data and Remove Equipment from a File System)

• stripe (Set the Stripe Width for a File System)

• suid (Mount a File System with setuid Execution Enabled)

• sw_raid (Turn On Software RAID Mode)

• sync_meta (Synchronize File System Metadata)

• trace (Enable File System Tracing)

Configuring Archival File Systems

The commands below control the archiving and staging behavior of Oracle HSM file systems:

• maxpartial (Set the Maximum Partial Release Size for the File System)

• nohwm_archive (Do Not Start Archiving at the High Water Mark)

• partial (Set the Default Partial Release Size for the File System)

• partial_stage (Set Partial Stage-Ahead Point for the File System)

• release (Release Archived Data Files and Disable Allocation on a Device)

• stage_flush_behind (Set the Stage Flush Behind Size)

• stage_n_window (Size the Buffer for Reading Directly from Archival Media)

• thresh (Set High and Low Watermarks)

Configuring Shared File Systems

The following commands control how Oracle HSM coordinates interactions between hosts that share a file system.

• aplease (Set Append Lease Expiration Time for a Shared File System)

• lease_timeo (Set the Unused Lease Timeout for a Shared File System)

• maxallocsz (Set the Maximum Allocation Size for a Shared File System)

• mh_write (Turn on Multi-Host Read/Write)

• minallocsz (Set the Minimum Allocation Size for a Shared File System)

• min_pool (Set the Minimum Number of Shared File System Threads)

• nomh_write (Turn Off Multi-Host Read/Write)

• rdlease (Set the Read Lease Time for a Shared File System)

• wrlease (Set the Write Lease Time for a Shared File System)

Configuring Single-Writer/Multi-Reader File Systems

The commands below control how and when a read-only host obtains metadata updates from the metadata server.

• invalid (Set the Invalidate-Cache Delay for a Multi-Reader File System)

• norefresh_at_eof (Do Not Refresh at EOF in a Multi-Reader File System)

• refresh_at_eof (Refresh at EOF in a Multi-Reader File System)

Configuring File Systems for Oracle Real Application Clusters (RAC)

The following commands are specific to implementations of Oracle Real Application Clusters (RAC) that store data on Oracle HSM file systems using asynchronous I/O and Solaris Volume Manager mirrored volumes.

• abr (Enable Application Based Recovery)

• dmr (Enable Directed Mirror Reads of Software Mirrors)

• noabr (Disable Application Based Recovery)

• nodmr (Disable Directed Mirror Reads of Software Mirrors)

Managing Storage Devices

• alloc (Enable Storage Allocation on a Device)

• clear (Clear a Load Request for a Removable Storage Volume)

• devlog (Set Device Logging Options)

• idle (Idle Device)

• noalloc (Disable Storage Allocation on a Device)

• off (Turn Off A Device)

• on (Turn On A Device)

• readonly | ro (Make Device Read Only)

• unavail (Make a Device Unavailable to Oracle HSM)

Managing Robotic Storage Libraries

• audit (Audit Library or Library Slot)

• export (Move Removable Media to the Robotic Library's Mailbox)

• import (Move Removable Media from the Mailbox into the Robotic Library)

• load (Load a Cartridge into a Drive)

• priority (Set Priority in Load-Request Preview Queue)

• unload (Unload a Drive)

Archiving

• aridle (Stop Archiving Gracefully)

• arrerun (Restart the Archiver Non-Disruptively)

• arrestart (Restart the Archiver Disruptively)

• arrmarchreq (Remove Archive Requests)

• arrun (Start Archiving)

• arscan (Scan a File System for Unarchived Files)

• arstop (Stop All Archiving Immediately)

• artrace (Perform Archiver Tracing)

Staging

• stclear (Clear a Stage Request)

• stidle (Stop Staging as Soon as Possible)

• strun (Start Staging)

Working with Service and Support Representatives

The samu interface includes a number of commands that are designed to help you assist Oracle technical support and service representatives. These handle the following tasks:

• Controlling Diagnostic Displays

• Gathering Diagnostic Information

Controlling Diagnostic Displays

The samu service and support display commands are designated by uppercase letters: C, D, F, I, J, K, L, M, N, P, R, S, T, and U. They provide debugging and internal state information that is not generally useful without the assistance of a member of the Oracle technical support staff.

• :C (Display the Contents of Shared Memory at a Specified Address)

• D (Display Disk Volume Dictionary Screen)

• F (Display Optical Disk Label Screen)

• I (Display Inode Information)

• J (Display the Shared Memory Segment for the Load-Request Preview Queue)

• K (Display Kernel Statistics)

• L (Display Shared Memory Tables and System Defaults)

• M (Display Raw Shared Memory)

• N (Display File System Parameters)

• P (Display Active Services)

• R (Display SAM-Remote Configuration Information)

• S (Display Raw Sector Data)

• T (Display SCSI Sense Data for a Current or Specified Device)

• U (Display Device Table in Human-Readable Form)

Gathering Diagnostic Information

• diskvols (Set/Clear Flags on Disk Volumes Used for Archiving)

• dtrace (Enable/Configure Tracing for Oracle HSM Daemons)

• open (Open a Disk Storage Device for Reading)

• read (Read Sectors On a Disk Storage Device)