ORA-00821: Specified value of sga_target 3072M is too small, needs to be at least 12896M

oerr ora 00821
00821, 00000, "Specified value of sga_target %sM is too small, needs to be at least %sM"
// *Cause: The specified value of sga_target is too small for the SGA to
// accommodate all of the necessary SGA components such as the
// log buffer, buffer pools, shared pool, etc.
// *Action: Set sga_target to the recommended value or reduce the values
// of any SGA component size parameters you have specified.


由于资源有限，克隆过来的数据库服务器只给了9G的内存，结果在测试时，老是会出现 OOMkiller导致宕机,即 out of memory killer,是linux下面当内存耗尽时的的一种处理机制。

当内存较少时，OOM会遍历整个进程链表，然后根据进程的内存使用情况以及它的oom score 值最终找到得分较高的进程，然后发送kill信号将其杀掉。

于是调整了一下sga_target和sga_max_size这两个参数，结果重启的时候悲剧了:

sqlplus / as sysdba

SQL> startup
ORA-00821: Specified value of sga_target 3072M is too small, needs to be at least 12896M
SQL> startup nomount
ORA-00093: _shared_pool_reserved_min_alloc must be between 4000 and 0

出现这个这个错误，突然想起来这个服务器设置过shared_pool_size参数，于是生成pfile，检查initGSP.ora，如下所示，
SQL> create pfile='/u01/app/oracle/product/10.2.0/db_1/dbs/initGSP.ora' from spfile;


手工将.shared_pool_size设置为0， 然后启动数据库实例，问题解决。如下所示：
SQL> startup pfile='/u01/app/oracle/product/10.2.0/db_1/dbs/initGSP.ora'