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For 64-bit c-treeACE servers, a timeout allows each thread to detect and perform its own disconnection in case of a timeout.
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When more than one FairCom Server was run on a Unix system, the shared memory keys used by different servers could have the same value, which prevented connections to the servers. In addition, it was possible for unrelated applications to collide with default keys generated by c-treeACE servers.
To address this key collision, it is now possible for an administrator to specify specific shared memory keys for ISAM and SQL shared memory communication protocols ensuring the keys do not match existing keys already in use on the system.
New FairCom Server configuration options are available to directly specify a shared memory key. SQL and ISAM each require separate shared memory support
SHMEM_KEY_ISAM <isam_shared_memory_key>
SHMEM_KEY_SQL <sql_shared_memory_key>
Shared memory key values can be specified in either decimal or hexadecimal format. For example:
; Set shared memory key for ISAM connections to the specified decimal value:
SHMEM_KEY_ISAM 12345
; Set shared memory key for ISAM connections to the specified hexadecimal value:
SHMEM_KEY_ISAM 0xabcd
These server configuration options support specifying an environment variable, whose value is substituted for the configuration option value when the server starts up. For example, if the environment variable MY_ISAM_KEY is set to a numeric value such as 12345 or 0xabcdef before starting the server process, then the following option can be specified in the server configuration file to use this environment variable value for the SHMEM_KEY_ISAM configuration option value:
SHMEM_KEY_ISAM %MY_ISAM_KEY%
Compatibility Notes:
When these configuration options are not used, FairCom Server uses the old method of assigning shared memory keys so its shared memory communication protocol is compatible with old clients. FairCom Server now writes the shared memory key to the shared memory resource file and new clients know to read the shared memory key from this file. If a new client finds no shared memory key in the file, it uses the old method to assign a shared memory key so it is compatible with an old server.
The shared memory resource file is named /tmp/ctreedbs/<server_name> for ISAM, and /tmp/ctreedbs/CTSQL_<sql_port> for SQL, where /tmp/ctreedbs is the default shared memory directory. It can be changed using the SHMEM_DIRECTORY configuration option.
An old client will not be able to connect to a new server using shared memory if the server uses the SHMEM_KEY_ISAM or SHMEM_KEY_SQL configuration option to specify a shared memory key that differs from the shared memory key that the old method would generate.
