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Valid for AIX JFS file systems only
In an AIX JFS environment, the HSM client provides the following two additional recall modes that recall a migrated file to its originating file system:
These recall modes are for read access on migrated files only. You cannot set a recall mode for a resident or a premigrated file.
Attention: Do not use the migrate-on-close or read-without-recall mode for a file that you migrate from a file system that an NFS server exports. Because NFS opens and closes a file many times when an NFS client accesses it, performance can be severely hindered.
To set or change recall modes on your migrated files, use the dsmattr command. The recall mode that you set for a migrated file remains associated with that file only as long as the file remains migrated. See "Use the dsmattr Command" for more information about this command.
If you change the recall mode for a migrated file, or for a specific execution of a recall process, you change how the HSM recall daemon recalls a migrated file. See "Use the dsmmode Command" for more information about this command.
If you recreate a deleted stub file, the recall mode for the file becomes normal (the default) despite what you previously set.
You can access a file using more than one process at a time. Another process can cause a file that you are accessing in migrate-on-close or read-without-recall mode to remain on your local file system as a resident or premigrated file. For example, if you set the recall mode to normal (the default) for a migrated file, and you access it with a process using the migrate-on-close recall mode and you do not modify the file, you would expect the file to be in a migrated state when you close it. But if someone else accesses the file at the same time with a process using normal recall mode or with a process that modifies the file in some way, the file remains on your local file system as either a resident or a premigrated file, depending on the actions that the other process takes.
Valid for AIX JFS file systems only
The migrate-on-close mode temporarily recalls a migrated file to its originating file system. The recalled file remains on your local file system for as long as it remains open. If you do not modify the file before you close it, the HSM client replaces it with a stub file on your local file system. It then becomes a migrated file. The copy that currently resides in TSM storage remains valid because you did not modify the file. If more than one process accesses the file at one time, the HSM client returns the file to a migrated state only if all the processes do not modify the file. If any one process modifies the file, it remains on your local file system as a resident file.
Use the dsmattr command to set the recall mode to migrate-on-close for migrated files that you normally read but that you do not modify. When you set the recall mode to migrate-on-close, this mode remains associated with your files until you:
For more information about changing recall modes on migrated files, see "Use the dsmattr Command".
Valid for AIX JFS 4.3 file systems only
The read-without-recall mode reads a migrated file from TSM storage without storing it on your local file system. The HSM client reads information sequentially from the migrated file, and caches that information in a memory buffer on your workstation. This occurs either when the processes that access the file do not modify it, or when the file is executable but the process does not execute the file. If the file is a binary executable file, the file is recalled to your local file system if a process executes it. The file remains on your local file system as a premigrated file or it is returned to a migrated state, depending on which recall mode the process used that stored it on your local file system.
Attention: Do not set the read-without-recall mode on a file that an NFS server exports. This attribute holds recalled file data in memory. It is not compatible with NFS access, which uses asynchronous reads. If you accidentally set this attribute on a file that a remote NFS client accesses, the HSM client recalls the file and automatically sets the recall attribute of the file to normal.
When you use the read-without-recall mode, the following actions can occur:
Use the read-without-recall mode for single access, sequential reads of non-executable files. Accessing a read-without-recall file with more than one process at the same time, or seeking backward in a file can significantly affect the performance of each process that accesses your files. Each of these actions can cause the HSM client to break the connection with the TSM server and start the read-without-recall process again. Each read process in progress for the file is delayed until the next piece of information it needs is cached in a memory buffer. Only a small portion of a read-without-recall file is cached in a memory buffer to keep to a minimum the memory overhead of read-without-recall files.
Using the read-without-recall mode to access more than one file can cause a conflict for resources on the TSM server. For example, if a single process opens more than one file, and those files reside on the same sequential media, the process obtains access to only one file at a time. If a process reads only the first megabyte of data from each file, and it leaves the files open for additional reads later, one or more of the reads can time out if the process has been waiting too long, and the TSM server must free resources to perform the next read.
When you set the recall mode for a migrated file to read-without-recall, that mode remains associated with your file until you:
If a file is a binary executable file and you run it with execute permission, the recall mode is normal.
Table 13 displays the recall mode that is used depending on the:
If the recall mode for a migrated file is: | And the recall mode for a process is: | If the process: | This recall mode is used: |
---|---|---|---|
Normal | Normal | Does not modify the file | Normal. File becomes premigrated. |
Normal | Normal | Modifies the file | Normal. File becomes resident. |
Normal | Migrate-on-close | Does not modify the file | Migrate-on-close. File returned to migrated state. |
Normal | Migrate-on-close | Modifies the file | Normal. File becomes resident. |
Migrate-on-close | Normal | Does not modify the file | Migrate-on-close. File returned to migrated state. |
Migrate-on-close | Normal | Modifies the file | Normal. File becomes resident. |
Migrate-on-close | Migrate-on-close | Does not modify the file | Migrate-on-close. File returned to migrated state. |
Migrate-on-close | Migrate-on-close | Modifies the file | Normal. File becomes resident. |
Read-without-recall | Normal | Does not:
| Read-without-recall. File remains migrated. |
Read-without-recall | Normal |
| Normal. If modified, file becomes resident. If not modified, file becomes premigrated. |
Read-without-recall | Migrate-on-close | Does not:
| Read-without-recall. File remains migrated. |
Read-without-recall | Migrate-on-close |
| Migrate-on-close. File returns to migrated state. |
Read-without-recall | Migrate-on-close | Modifies the file | Normal. File becomes resident. |