wiki:manuals/SpaceReservationStatic
Last modified 14 years ago Last modified on 08/29/07 19:23:19

Using default Spaces

or :

How to write files with SRM 2.2 without specifying a space token.

Just for this description I would like to define some expressions with might be wrong in general but help to understand the matter.

A file in dCache always has a fixed set of attributes which determine its behaviour on disk and on tape. Currently those attribues are the retention policy and the access latency. In order to define those attributes for a file, they have to be specified while writing this file to dCache. This can be done explicitly by specifing the appropriate values for those parameters in the SRM prepare to put call or implicitly by providing a so called space token to the prepare to put call. This token actually has, when being created, the same attributes attached. In fact, the token represents a bit more than just those attributes. It has a maximum number of bytes defined which is allowed to written into this token.

In order to find the right space attributes resp. space The default space attributes are set in the dCacheSetup file.

Please check :

# # ----if space reservation request does not specify retention policy # we will assign this retention policy by default # SpaceManagerDefaultRetentionPolicy?=CUSTODIAL # # ----if space reservation request does not specify access latency # we will assign this access latency by default # SpaceManagerDefaultAccessLatency?=NEARLINE

These are the attributes used if neither a space token, nor

space attributes (AL/RP) are given. dCache will take those defaults and will check for a linkGroup matching those AL/RP plus the vogroup information. It will then dynamically generate a space token and will use this token for the transfer. This is done opaque. So you will not notice that a token has been generated.

cheers

patrick